# Synthetic motor oil- worth it for me? **URL:** \ **Category:** Factual Questions\ **Created:** [February 28, 2006, 6:20am UTC](https://boards.straightdope.com/t/synthetic-motor-oil-worth-it-for-me/346425 "2006-02-28T06:20:00Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![Rick](https://avatars.discourse-cdn.com/v4/letter/r/9f8e36/32.png) [@Rick](https://boards.straightdope.com/u/Rick)\ **Post date:** [March 1, 2006, 10:32pm UTC](https://boards.straightdope.com/t/synthetic-motor-oil-worth-it-for-me/346425/21 "2006-03-01T22:32:36Z")
> [@Rocketeer](#): > > Wow, that’s a lot! Most of the cars I’ve had take about four. Is it an air-cooled Porsche? Nope late model Volvo. depending on the model the oil level runs 6.5-7 qts. ---
**Author:** ![ombre3](https://avatars.discourse-cdn.com/v4/letter/o/da6949/32.png) [@ombre3](https://boards.straightdope.com/u/ombre3)\ **Post date:** [March 2, 2006, 3:47am UTC](https://boards.straightdope.com/t/synthetic-motor-oil-worth-it-for-me/346425/22 "2006-03-02T03:47:16Z")
> [@Rick](#): > > Sorry but your math does not hold up. My engine holds about 7 quarts. It uses about 1 quart of oil every 8,000 miles or so. In 30,000 miles, I will have had to add about 3 quarts, less than 1/2 of an oil change. > Plus adding oil does not do anything for the gunk still in the crankcase. Well-----I am going by my own personal experience with cars----that hold 4 quarts. Best one I ever had used a quart every 3000 miles. Otherwise, on my other cars----not even close. A quart every 1500 miles or 1000 miles usage very normal for an American car. My math is excellent for my experience. ---
**Author:** ![ombre3](https://avatars.discourse-cdn.com/v4/letter/o/da6949/32.png) [@ombre3](https://boards.straightdope.com/u/ombre3)\ **Post date:** [March 2, 2006, 4:02am UTC](https://boards.straightdope.com/t/synthetic-motor-oil-worth-it-for-me/346425/23 "2006-03-02T04:02:00Z")
> [@ombre3](#): > > Well-----I am going by my own personal experience with cars----that hold 4 quarts. Best one I ever had used a quart every 3000 miles. Otherwise, on my other cars----not even close. A quart every 1500 miles or 1000 miles usage very normal for an American car. > > My math is excellent for my experience. Probably should explain the cars I am talking about— 39 Plymouth Coupe, 63 Ford Galaxie, 66 Ford Mustang, 72 Dodge Dart, 73 Plymouth Valiant, 76 Dodge Dart, 83 Buick Regal, 84 Camaro, 88 Camaro, 95 Jeep Cherokee. The 2 best in oil consumption were the 63 Ford Galaxie and the 95 Jeep Cherokee—Used a quart of oil in 3000 to 4000 miles. The rest were much less than that ----about 1500 was normal. Newer cars may be better in oil consumption. But I doubt it as a general rule. ---
**Author:** ![Mr.Slant](https://avatars.discourse-cdn.com/v4/letter/m/c57346/32.png) [@Mr.Slant](https://boards.straightdope.com/u/Mr.Slant)\ **Post date:** [March 2, 2006, 4:04am UTC](https://boards.straightdope.com/t/synthetic-motor-oil-worth-it-for-me/346425/24 "2006-03-02T04:04:19Z")
> [@ombre3](#): > > SNIP > Newer cars may be better in oil consumption. But I doubt it as a general rule. My '02 Sable has used less than half a quart of oil since my last oil change. The oil is now at 9,824 miles and is getting changed tomorrow afternoon. ---
**Author:** ![ombre3](https://avatars.discourse-cdn.com/v4/letter/o/da6949/32.png) [@ombre3](https://boards.straightdope.com/u/ombre3)\ **Post date:** [March 2, 2006, 4:08am UTC](https://boards.straightdope.com/t/synthetic-motor-oil-worth-it-for-me/346425/25 "2006-03-02T04:08:24Z")
And the gunk in the bottom of the crankcase is at the bottom of the crankcase, because it is heavier (DUH.) It will pretty much stay there. If it doesn’t —that is what they make filters for. ---
**Author:** ![ombre3](https://avatars.discourse-cdn.com/v4/letter/o/da6949/32.png) [@ombre3](https://boards.straightdope.com/u/ombre3)\ **Post date:** [March 2, 2006, 4:12am UTC](https://boards.straightdope.com/t/synthetic-motor-oil-worth-it-for-me/346425/26 "2006-03-02T04:12:36Z")
> [@Mr. Slant](#): > > My '02 Sable has used less than half a quart of oil since my last oil change. > The oil is now at 9,824 miles and is getting changed tomorrow afternoon. I have already admitted that newer motors may do better with oil consumption. Though I did doubt it generally, (admit it could be true in isolated specific cases) Let’s have more input here to see if I have any validity at all in what I stated. All you teeming millions out there driving modern cars– What is your oil consumption? ---
**Author:** ![Mr.Slant](https://avatars.discourse-cdn.com/v4/letter/m/c57346/32.png) [@Mr.Slant](https://boards.straightdope.com/u/Mr.Slant)\ **Post date:** [March 2, 2006, 5:09am UTC](https://boards.straightdope.com/t/synthetic-motor-oil-worth-it-for-me/346425/27 "2006-03-02T05:09:45Z")
> [@ombre3](#): > > I have already admitted that newer motors may do better with oil consumption. Though I did doubt it generally, (admit it could be true in isolated specific cases) > > Let’s have more input here to see if I have any validity at all in what I stated. > > All you teeming millions out there driving modern cars– > > What is your oil consumption? Oooh. Dundo dat. Open a thread in MPSIMS, which is where people will expect a poll! ---
**Author:** ![Mr.Slant](https://avatars.discourse-cdn.com/v4/letter/m/c57346/32.png) [@Mr.Slant](https://boards.straightdope.com/u/Mr.Slant)\ **Post date:** [March 2, 2006, 6:05am UTC](https://boards.straightdope.com/t/synthetic-motor-oil-worth-it-for-me/346425/28 "2006-03-02T06:05:48Z")
> [@bigurn](#): > > Really folks, 30K between changes is normal for me with a product like Mobil 1. My Mazda is new, but the minivan I referred to has had two oil changes, and it just turned 60,000 miles. I also own a daily driver Dodge Neon with 183,000 (no, not a typo) miles on it. If any car needs help living a long life, it’s a Neon. Still, 30K between changes for the past 8 years. [Not for everyone.](http://groups.google.com/group/alt.autos.toyota/browse_thread/thread/7c3a0970736383ea/f42c1efd92cec757%23f42c1efd92cec757?sa=X&oi=groupsr&start=0&num=2) ---
**Author:** ![Rick](https://avatars.discourse-cdn.com/v4/letter/r/9f8e36/32.png) [@Rick](https://boards.straightdope.com/u/Rick)\ **Post date:** [March 2, 2006, 6:13am UTC](https://boards.straightdope.com/t/synthetic-motor-oil-worth-it-for-me/346425/29 "2006-03-02T06:13:14Z")
Not going for the poll, but a way to explain. Modern cars use a device called an Idle Air Contol Valve (IACV) to regulate the idle speed. This valve also limits the amount of vacuum in the intake manifold during decleration. Limiting the vacuum limits the amount of oil pulled past the rings and valve seals vastly reducing the amount of oil used in an engine. Thinking back over the years, it has been maybe 15 years since I had a car that did not get at least 5,000 miles per quart. A 1939 Plymouth is not what is in showrooms now (or what has been there for the last 15-20 years) I stand by my comments. ---
**Author:** ![Lightray](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lightray/32/391_2.png) [@Lightray](https://boards.straightdope.com/u/Lightray)\ **Post date:** [March 2, 2006, 2:26pm UTC](https://boards.straightdope.com/t/synthetic-motor-oil-worth-it-for-me/346425/30 "2006-03-02T14:26:14Z")
> [@ombre3](#): > > And the gunk in the bottom of the crankcase is at the bottom of the crankcase, because it is heavier (DUH.) > > It will pretty much stay there. If it doesn’t —that is what they make filters for. The gunk that is accumulating at the bottom of your crankcase is why there are dispersants in engine oils – because that gunk is supposed to be dispersed in the oil by the dispersant (duh), and then carried out when you change your oil. If you’re accumulating gunk, then you’ve kept the oil in service longer than its dispersancy can handle. Hence, the gunk is settling out. Filters are not designed to handle the extra load from operating past the performance capability of your engine oil. ---
**Author:** ![ombre3](https://avatars.discourse-cdn.com/v4/letter/o/da6949/32.png) [@ombre3](https://boards.straightdope.com/u/ombre3)\ **Post date:** [March 2, 2006, 3:12pm UTC](https://boards.straightdope.com/t/synthetic-motor-oil-worth-it-for-me/346425/31 "2006-03-02T15:12:46Z")
> [@Lightray](#): > > The gunk that is accumulating at the bottom of your crankcase is why there are dispersants in engine oils – because that gunk is supposed to be dispersed in the oil by the dispersant (duh), and then carried out when you change your oil. > > If you’re accumulating gunk, then you’ve kept the oil in service longer than its dispersancy can handle. Hence, the gunk is settling out. > > Filters are not designed to handle the extra load from operating past the performance capability of your engine oil. You are right of course. I threw that one in there without giving it much thought. ---
**Author:** ![ombre3](https://avatars.discourse-cdn.com/v4/letter/o/da6949/32.png) [@ombre3](https://boards.straightdope.com/u/ombre3)\ **Post date:** [March 2, 2006, 3:17pm UTC](https://boards.straightdope.com/t/synthetic-motor-oil-worth-it-for-me/346425/32 "2006-03-02T15:17:13Z")
> [@Rick](#): > > Not going for the poll, but a way to explain. Modern cars use a device called an Idle Air Contol Valve (IACV) to regulate the idle speed. This valve also limits the amount of vacuum in the intake manifold during decleration. Limiting the vacuum limits the amount of oil pulled past the rings and valve seals vastly reducing the amount of oil used in an engine. > Thinking back over the years, it has been maybe 15 years since I had a car that did not get at least 5,000 miles per quart. A 1939 Plymouth is not what is in showrooms now (or what has been there for the last 15-20 years) > I stand by my comments. Actually a 39 Plymouth hasn’t been in showrooms for 67 years-----so probably a poor example there. I am curious about the 95 Jeep Cherokee though-----only about 11 years old. I thought it does great as far as oil consumption--------only used a quart in 4000 miles----which I thought was exceptional, at least in my experience. So does a 95 Jeep Cherokee with 4.0 have that IACV? If so, was one quart per 4000 miles excessive? (Meaning of course I should be damning the Jeep, rather than praising it.) ---
**Author:** ![ralph124c](https://avatars.discourse-cdn.com/v4/letter/r/8797f3/32.png) [@ralph124c](https://boards.straightdope.com/u/ralph124c)\ **Post date:** [March 2, 2006, 3:51pm UTC](https://boards.straightdope.com/t/synthetic-motor-oil-worth-it-for-me/346425/33 "2006-03-02T15:51:45Z")
All engine oils are susceptible to sludging. which means that under the intense heat of engine operation, the oil oidizes and forms sluge-a combination of water, sulphuric acid, carbonized oil. Sludge blocks the filter, and will eventuallu block the oil passages in the engine…leading to bearing failure and a blown engine. I’ve heard that certain cars (like turbocharges Audi A4 engines0 are susceptible to sludge formation, in as little as 3000 miles. hence, even if you use synthtic, you must change the oil more frequently, or rish losing your engine. So what is a safe oilchange interval? ---
**Author:** ![tygerbryght](https://avatars.discourse-cdn.com/v4/letter/t/a9a28c/32.png) [@tygerbryght](https://boards.straightdope.com/u/tygerbryght)\ **Post date:** [March 2, 2006, 4:25pm UTC](https://boards.straightdope.com/t/synthetic-motor-oil-worth-it-for-me/346425/34 "2006-03-02T16:25:37Z")
Piggybacking on the thread: I just bought a 98 Dodge Dakota. It has just over 200k miles, was one of a local company’s service vehicles. It looks & runs _far_ better than the average vehicle of that age & mileage (or I wouldn’t have bought it). I just need something to get me to the supermarket and to medical appointments, so I don’t expect to be doing much driving. I don’t want to have to trade for at least the next several years. Any advice? It’s a 4-banger with a stick shift, in case anybody needs that information. I’ve got the manual, but not the service history. My last long-term vehicle was an 87 Mustang (sold in 98) with ditto drivetrain. I’ve always believed in religiously followinig the 3k oil change mantra. I don’t think they’ve been using synthetic oil, as there’s a sticker from one of those places for my next oil change. ---
**Author:** ![Pork\_Rind](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pork_rind/32/111_2.png) [@Pork\_Rind](https://boards.straightdope.com/u/Pork_Rind)\ **Post date:** [March 2, 2006, 4:46pm UTC](https://boards.straightdope.com/t/synthetic-motor-oil-worth-it-for-me/346425/35 "2006-03-02T16:46:37Z")
> [@Mr. Slant](#): > > The BMW is basing its decision to ask for an oil change on a fairly sophisticated algorithm that includes paying a lot of attention to facts like hours of operation, throttle settings, operating temperatures and gobs of other factors the car’s computer has access to. It’s not rolling a pair of twenty-sided dice under the hood and then consulting a chart. > The algorithm also assumes you’re running a certain kind of synthetic. Consult owner’s manual for specifics, but I’m thinking ACEA A3 or ACEA A5. Make SURE you don’t deviate from that specification when you change the oil, or you’ll turn that BMW into a $30K motor oil failure research lab. > GM has a similar system on most of its cars and some of its trucks. > DaimlerChrysler uses a system (mostly on Mercedes models, IIRC) that relies on an algorithm and a primitive built-in oil tester. I think the oil tester basically measures the oil’s electrical conductivity. Oh, I know how it works. This is the second BMW with this setup that we’ve had. With our previous BMW, I even proposed to the service advisor that maybe we should change the oil ‘early’ at 10k miles. He looked at me like possibly I’d grown a third eye and said, “Don’t waste your money.” And as a data point, that 3 series used just under a quart in 15,000 miles. ---
**Author:** ![Lightray](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lightray/32/391_2.png) [@Lightray](https://boards.straightdope.com/u/Lightray)\ **Post date:** [March 2, 2006, 5:08pm UTC](https://boards.straightdope.com/t/synthetic-motor-oil-worth-it-for-me/346425/36 "2006-03-02T17:08:04Z")
> [@ralph124c](#): > > So what is a safe oilchange interval? It really does vary from car to car, and from oil to oil. In _most_ cars, using oils that are ILSAC certified, 3000 miles is far too early. You could double that with no problem. Triple, if you’re using synthetic, and you’re probably okay. From what I’ve seen, I would take the car manufacturer’s recommendation as a starting point only. They’re good at spec’ing out what they want in their oil performance – but they spec that performance using engine tests that don’t always match what actually happens in the car (and are often notoriously non-repeatible). Instead, talk to your mechanic or whoever is changing your oil. If the spent oil is coming out dark and sludgy, change your oil earlier next time. If it looks like the stuff you’re pouring out of the quart bottle, you’re way too early changing it. Heavy duty users of motor oil (truck fleets, etc.) will be set up to test their oil for degradation – usually pH, occasionally some other indicators (viscosity or water content) – and change the oil once those indicators start to go sour (when they’ve used up all the active additives in the oil). Probably a bit too expensive for passenger car use, unless you have something that’s _really_ costly. Unfortunately, I’m not involved in formulations, so I’m not familiar with the differences between the various manufacturers and car models. If you’ve got a vehicle that’s likely to need a different oil change schedule (e.g., high performance cars), I’d just recommend changing early or at the manufacturer’s recommendation at first, then backing off as you see how your oil usage goes. ---
**Author:** ![Rick](https://avatars.discourse-cdn.com/v4/letter/r/9f8e36/32.png) [@Rick](https://boards.straightdope.com/u/Rick)\ **Post date:** [March 3, 2006, 3:22am UTC](https://boards.straightdope.com/t/synthetic-motor-oil-worth-it-for-me/346425/37 "2006-03-03T03:22:11Z")
> [@ombre3](#): > > Actually a 39 Plymouth hasn’t been in showrooms for 67 years-----so probably a poor example there. > > I am curious about the 95 Jeep Cherokee though-----only about 11 years old. I thought it does great as far as oil consumption--------only used a quart in 4000 miles----which I thought was exceptional, at least in my experience. > > So does a 95 Jeep Cherokee with 4.0 have that IACV? If so, was one quart per 4000 miles excessive? > > (Meaning of course I should be damning the Jeep, rather than praising it.) The 15-20 years was a note about how long moden fuel injected cars have been around. :smack: Does you '95 Jeep have an IACV? Probably. Is a quart in 4,000 excessive for this engine? Maybe, maybe not. Since I don’t have any experience on Jeeps, I don’t know if your number is low or high compared to other Jeeps with this engine. Because different engines use different piston designs, piston ring designs, valve guide clearances and type of valve seals used some engines will use more oil that others. If you really want to know, surf around the net. I’m sure there is at least one Jeep owner’s board where you can get some idea of what other guys are getting. ---
**Author:** ![ombre3](https://avatars.discourse-cdn.com/v4/letter/o/da6949/32.png) [@ombre3](https://boards.straightdope.com/u/ombre3)\ **Post date:** [March 3, 2006, 4:31am UTC](https://boards.straightdope.com/t/synthetic-motor-oil-worth-it-for-me/346425/38 "2006-03-03T04:31:05Z")
> [@Rick](#): > > The 15-20 years was a note about how long moden fuel injected cars have been around. :smack: > Does you '95 Jeep have an IACV? Probably. > Is a quart in 4,000 excessive for this engine? Maybe, maybe not. Since I don’t have any experience on Jeeps, I don’t know if your number is low or high compared to other Jeeps with this engine. Because different engines use different piston designs, piston ring designs, valve guide clearances and type of valve seals used some engines will use more oil that others. > If you really want to know, surf around the net. I’m sure there is at least one Jeep owner’s board where you can get some idea of what other guys are getting. When the Jeep was new it used only about a quart every 4000 miles. It now has 160,000 miles on it and is down to 1 quart every 2000 miles. Have always used dino oil, changed regularly at 4000 miles.--------because it was down a quart. (Always change the filter every oil change.) Now change it at 3000 miles, because it is down about a quart and a half. (5 quart crankcase on this one—so still works for me because I don’t think that hurts anything on that large a crankcase, oil filled) I think that is exceptional. Of course I could be wrong. And I still do not understand the purpose of synthetic oil---------at least not in my experience. You can get excellent motor longevity using dino oil, and changing it and the filter regularly. (3 to 4 thousand miles.) As has been previously stated —mileage advantage of synthetic is an illusion. So what is the purpose of synthetic oil, besides making people spend more bucks? ---
**Author:** ![Mr.Slant](https://avatars.discourse-cdn.com/v4/letter/m/c57346/32.png) [@Mr.Slant](https://boards.straightdope.com/u/Mr.Slant)\ **Post date:** [March 3, 2006, 4:54am UTC](https://boards.straightdope.com/t/synthetic-motor-oil-worth-it-for-me/346425/39 "2006-03-03T04:54:13Z")
> [@ombre3](#): > > SNIP > As has been previously stated —mileage advantage of synthetic is an illusion. > > So what is the purpose of synthetic oil, besides making people spend more bucks? Synthetic 0W30 starts nicely at -40 F. Conventional 0W30 does not exist. Mobil 1 can survive for extended periods above 300 degrees fahrenheit. Conventional oil begins failing rather quickly at that point. Those are the biggest two reasons for synthetic. Neither applies to 99% of consumers. ---
**Author:** ![Rick](https://avatars.discourse-cdn.com/v4/letter/r/9f8e36/32.png) [@Rick](https://boards.straightdope.com/u/Rick)\ **Post date:** [March 3, 2006, 5:11am UTC](https://boards.straightdope.com/t/synthetic-motor-oil-worth-it-for-me/346425/40 "2006-03-03T05:11:26Z")
Mr. Slant has a very good answer. But, **ombre** you might want to cruise over to [this thread\*](http://boards.straightdope.com/sdmb/showthread.php?t=352827&highlight=synthetic+motor) and read posts 19 & 20. Make sure to read the links in post #19. This should help explain why snythetics are needed for some engines. \*Sorry, but I have a killer headache right now, and I am not in a mood to recreate what I have already written. [Previous page](https://boards.straightdope.com/t/synthetic-motor-oil-worth-it-for-me/346425.md?page=1) [Next page](https://boards.straightdope.com/t/synthetic-motor-oil-worth-it-for-me/346425.md?page=3)