# motor oil **URL:** \ **Category:** Factual Questions\ **Created:** [August 14, 2000, 12:58am UTC](https://boards.straightdope.com/t/motor-oil/29232 "2000-08-14T00:58:04Z")\ **Posts on this page:** 18\ **Page:** 2
**Author:** ![handy](https://avatars.discourse-cdn.com/v4/letter/h/b5a626/32.png) [@handy](https://boards.straightdope.com/u/handy)\ **Post date:** [August 14, 2000, 2:53pm UTC](https://boards.straightdope.com/t/motor-oil/29232/21 "2000-08-14T14:53:20Z")
Easy. If its black, change it. If it’s brown, don’t change it. if you need it, add it. ---
**Author:** ![Doctor\_Jackson](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/doctor_jackson/32/32_2.png) [@Doctor\_Jackson](https://boards.straightdope.com/u/Doctor_Jackson)\ **Post date:** [August 14, 2000, 4:03pm UTC](https://boards.straightdope.com/t/motor-oil/29232/22 "2000-08-14T16:03:36Z")
Anthracite - I don’t have a link to post, but Consumer Reports did an in depth report on motor oils a year or two ago. They ran various engines for differing times between oil changes, then studied the engine and the old oil. The bottom line was that there was virtually no difference in engine protection between 3000 and 5000 miles. Minimal degradition began to show at about 6000 miles. Their advice, IIRC, was to change oil every 5000 miles, but waiting 6 or 7 K between changes wouldn’t hurt. “Every 3000 miles” is the oil industry equivalent of “lather, rinse, repeat”. It won’t hurt, but it ain’t really necessary. ---
**Author:** ![Gunslinger](https://avatars.discourse-cdn.com/v4/letter/g/4491bb/32.png) [@Gunslinger](https://boards.straightdope.com/u/Gunslinger)\ **Post date:** [August 14, 2000, 4:20pm UTC](https://boards.straightdope.com/t/motor-oil/29232/23 "2000-08-14T16:20:43Z")
> [@](#): > > \*Originally posted by Anthracite \* > \*\* > Una, the V8 gal. \*\* My V8’s bigger than yours :p. AMC 360 (5.9L)–and it changes its own oil. AMC V8s are famous for leaking–it’s the built-in frame rust prevention system ;)…but they’ve also been taken apart at 200,000+ miles and still showed the original cylinder honing marks. ---
**Author:** ![Una\_Persson](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/una_persson/32/346_2.png) [@Una\_Persson](https://boards.straightdope.com/u/Una_Persson)\ **Post date:** [August 14, 2000, 4:55pm UTC](https://boards.straightdope.com/t/motor-oil/29232/24 "2000-08-14T16:55:42Z")
> [@](#): > > \*Originally posted by Doctor Jackson \* > \*\*Anthracite - > > I don’t have a link to post, but Consumer Reports did an in depth report on motor oils a year or two ago. They ran various engines for differing times between oil changes, then studied the engine and the old oil. The bottom line was that there was virtually no difference in engine protection between 3000 and 5000 miles. Minimal degradition began to show at about 6000 miles. Their advice, IIRC, was to change oil every 5000 miles, but waiting 6 or 7 K between changes wouldn’t hurt. > > “Every 3000 miles” is the oil industry equivalent of “lather, rinse, repeat”. It won’t hurt, but it ain’t really necessary. \*\* Now that’s a legitimate response back. Click & Clack reported the same thing, and there were also studies by the SAE on this backing your position up. I know it probably has a minimal (if any) difference, but it makes me feel better, and I can easily afford it. I don’t agree with the term “waste” per se if it is a high-performance car that is driven in severe conditions. My maintenance manual says in severe conditions, oil changes are a 3000-mile interval event for my “high-performance” car, and I agree with it. I do agree with you, and admitted that it was a diminishing return. But to quote myself earlier, “I change mine in my Mustang every 3000 miles or **whenever I get bored** , whichever comes first.” I mean, what gal doesn’t want to spend a nice afternoon changing the oil, checking the car out, and fiddling around with her air tools? Changing the oil for me becomes a “3000 mile Service Inspection” of sorts also, and lets be get under the chassis and check everything out. In the last change, I found an emergency brake cable had come loose, and tightened it back up to avoid problems. Fun, fun, silly-willy! ---
**Author:** ![casdave](https://avatars.discourse-cdn.com/v4/letter/c/c6cbf5/32.png) [@casdave](https://boards.straightdope.com/u/casdave)\ **Post date:** [August 14, 2000, 5:23pm UTC](https://boards.straightdope.com/t/motor-oil/29232/25 "2000-08-14T17:23:15Z")
Just lately there has been an oil that ahs come onto the market that is supposedly made for old cars. Trying to keep cars of 60’s and 70’s pedigree, if that last is the right word, has become a large enough hobby for various small companies to make a living providing pattern parts. Is there any real basis for using this specially adapted oil? ---
**Author:** ![mrblue92](https://avatars.discourse-cdn.com/v4/letter/m/5daacb/32.png) [@mrblue92](https://boards.straightdope.com/u/mrblue92)\ **Post date:** [August 14, 2000, 5:31pm UTC](https://boards.straightdope.com/t/motor-oil/29232/26 "2000-08-14T17:31:01Z")
> [@](#): > > The bottom line was that there was virtually no difference in engine protection between 3000 and 5000 miles. Minimal degradition began to show at about 6000 miles. Do you remember if they made any comparison between synthetic and regular oil? Supposedly synthetic offers superior protection, but I’ve got to imagine it gets just as dirty… Any particular type they thought was better? I’ve heard complaints about Penzoil’s paraffin-based nature… Something else that I just thought of while we’re on the subject… Does motor oil have any sort of shelf-life? If I find a case of two or three year old Valvoline 10w30 in my garage, is it safe to use? What if it’s 5 or 10 years old? Any significant degradation in protection? ---
**Author:** ![cornflakes](https://avatars.discourse-cdn.com/v4/letter/c/9d8465/32.png) [@cornflakes](https://boards.straightdope.com/u/cornflakes)\ **Post date:** [August 14, 2000, 6:39pm UTC](https://boards.straightdope.com/t/motor-oil/29232/27 "2000-08-14T18:39:45Z")
casdave, Do you mean Valvoline’s new oil that’s made for older cars? > **[Cincinnati News, Sports and Things to Do | Cincinnati Enquirer](https://www.cincinnati.com)** > > Breaking Cincinnati news, traffic, weather and local headlines from The Cincinnati Enquirer newspaper. My take is that they added a “seal conditioner” (ie. something that softens up the seals), which I would consider to be a bad thing, since this might shorten the life of a seal. I don’t know what oil spec are in use over the pond, but in the US, we use the American Petroleum Institute (API) standards. These are labeled on the oil can as SA through SH (they may be up to SJ by now, but I couldn’t find anything on [api.org](http://api.org), and I don’t have an oil can in the house.) All motor grades must meet the lower grade requirements, though they may have eased this a while back for a grade improvement made for emissions a while back. In any case, the latest API grade is still better than the SC or SE oil used back in 1970 or so. ---
**Author:** ![bibliophage](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bibliophage/32/7615_2.png) [@bibliophage](https://boards.straightdope.com/u/bibliophage)\ **Post date:** [August 14, 2000, 6:53pm UTC](https://boards.straightdope.com/t/motor-oil/29232/28 "2000-08-14T18:53:46Z")
> [@](#): > > \*Originally posted by Anthracite \* > \*\* > > > [@](#): > > > > \*Originally posted by Debbie \* > > **I never add oil to my car and just wondered how long it would keep on running without it. The last time I put oil in it was last year or the year before I think** > > Without sounding too melodramatic Debbie, it really sounds like you are driving on borrowed time. Which is sad if true - oil changes and checking your level and adding oil are relatively little expense and hassle relative to having to buy a new engine, or a new car. > > It is _possible_ if you have a really god car (like a 1990’s Japanese car) that doesn’t burn hardly any oil that you may not have run low.\*\* I had to borrow my brother’s 1990 Toyota for a 300-mile trip, and **thank God** I checked the oil before I left. There was a tiny bit of thick black sludge at the bottom of the dipstick. If there had been time before I had to leave, I would have changed the oil myself. As it was, I added 3 qts. to bring it up to halfway between the **low** and **full** marks on the dipstick. When I asked him about it, he said it had been about a year since he checked the oil and two or three since he had it changed. He told me he was going to get it changed, but it was another month before he got around to it. I usually change my oil after 3000 miles. If it’s not convenient (i.e., if I’m 2000 miles from home), I’ll let it go to 6000, but never more. I change the oil filter only every 6000 miles. If I were using fully synthetic oil, I’d change oil and filter both at 6000 miles. I personally don’t think synthetic is worth the price difference. As mentioned by others above, the oil **must** be changed at least every six months. ---
**Author:** ![bibliophage](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bibliophage/32/7615_2.png) [@bibliophage](https://boards.straightdope.com/u/bibliophage)\ **Post date:** [August 14, 2000, 7:10pm UTC](https://boards.straightdope.com/t/motor-oil/29232/29 "2000-08-14T19:10:16Z")
[QUOTE] \*Originally posted by mrblue92 \* \*\* > [@](#): > > Does motor oil have any sort of shelf-life? If I find a case of two or three year old Valvoline 10w30 in my garage, is it safe to use? What if it’s 5 or 10 years old? Any significant degradation in protection? \*\* The shelf-life of motor oil is about 3 years, according to [this site](http://www.escape.ca/~dbrad/shelf.htm). That seems over-careful to me, but what do I know? > [@](#): > > The following are signs of storage instability in a lubricant: > > Settling out of the additives as a gel or sticky liquid > Floc or haze > Precipitates/solid material > Color change or haziness > Water contamination in a lubricant can be detected by a “milky” appearance of the product. The old round quart cans had a shorter shelf-life than the newer plastic containers. ---
**Author:** ![casdave](https://avatars.discourse-cdn.com/v4/letter/c/c6cbf5/32.png) [@casdave](https://boards.straightdope.com/u/casdave)\ **Post date:** [August 14, 2000, 7:18pm UTC](https://boards.straightdope.com/t/motor-oil/29232/30 "2000-08-14T19:18:43Z")
**Cornflakes** We use US AP standards they are near universal now as well as the 10W/40 format. I don’t really get involved too much with car oil being a bike type person so I don’t remember exactly who the manufacturer is. I was wondering if it had anything to do with the fact that older engines had larger tolerances than more modern ones i hadn’t thought about other issues such as seals. I do know that the recent car oils with friction modifiers are bad for most bikes because most have wet clutches and this type of oil buggers them grandly. ---
**Author:** ![Yeah](https://avatars.discourse-cdn.com/v4/letter/y/dbc845/32.png) [@Yeah](https://boards.straightdope.com/u/Yeah)\ **Post date:** [August 15, 2000, 2:14am UTC](https://boards.straightdope.com/t/motor-oil/29232/31 "2000-08-15T02:14:11Z")
I’ve been told that it was U.S. Air Force pollcy not to change the oil in some of its old prop planes (e.g., DC-3s); they just changed the filters regularly and topped off the oil. ---
**Author:** ![Satan](https://avatars.discourse-cdn.com/v4/letter/s/e9bcb4/32.png) [@Satan](https://boards.straightdope.com/u/Satan)\ **Post date:** [August 15, 2000, 3:08am UTC](https://boards.straightdope.com/t/motor-oil/29232/32 "2000-08-15T03:08:03Z")
I was just reading the Used Car issue of _Consumer Reports_ in a book store and it said in a blurb that the brand of oil you use doesn’t matter a bit - presumably synthetic or natural are just as irrelevant as the manufacturer - and it also said specifically that following the basic maintenance of your car - using the proper weight and changing it every 5k or 7.5k miles - was just fine according to tests. That said, I am choosing to listen to my mechanic on this one and compromise the following way: I will do the normal maintenance every 7,500 miles that the manual for my 1997 Toyota Corolla mandates, but every 3,750 miles (the halfway point between scheduled maintenance) I’ll pop in an oil change. With the coupons I always get, and the amount I drive, this comes to an extra $50 or so a year, a small sum to pay for peace of mind in a vehicle that is costing ten thousand plus dollars. I did it every 5,000 miles with my 1995 Ford Escort as long as I owned it (from 40-100,000 miles), which was what the manual said you should do - and never had any engine problems. * * * Yer pal, Satan [sub]TIME ELAPSED SINCE I QUIT SMOKING: Four months, six days, 1 hour, 4 minutes and 36 seconds. 5121 cigarettes not smoked, saving $640.22. Life saved: 2 weeks, 3 days, 18 hours, 45 minutes.[/sub] **_"Satan is not an unattractive person."_-Drain Bead** [sub]Thanks for the ringing endorsement, honey!\*[/sub] ---
**Author:** ![Homer](https://avatars.discourse-cdn.com/v4/letter/h/df788c/32.png) [@Homer](https://boards.straightdope.com/u/Homer)\ **Post date:** [August 15, 2000, 3:40am UTC](https://boards.straightdope.com/t/motor-oil/29232/33 "2000-08-15T03:40:02Z")
Anth, it’s threads like this that make me wish I were a lesbian. I drive a 1990 Cavalier Z24 (officially one of the top fifty prettiest cars ever built. 😛 ) and I change the oil every 7000 miles. The first few times I changed it after I got it, the oil felt a little gritty, but since then, it’s always been a light brown, just a smidge darker than new. I am hard as hell on this car, so I can only _imagine_ how tough the last owner was for the oil to look like that. I’ve also taken off the intake runners and cleaned the shit out of them, as well as using one of the best oil filters they carry around here (Fram DoubleGuard, and 5w-20 High Horsepower [forget the manufacturer] but I’ve been thinking about switching to a K&N, with RedLine oil). I’ve got about 132000 miles on this engine, no rust, perfect paint, only 2 small dents, never a mechanical problem yet, I’ve had it since just over 100000 miles. I’ve got a slight shimmy from a wearing wheel bearing, but I don’t think I’ll fix it _juuust yet_ cuz I don’t have $75 for the new one. “We don’t sell bearings to press in. We only sell the whole unit.” they tell me. Bah. I’ll probably just swap out the one from the 5 speed I’m getting (hopefully tomorrow… _crosses fingers_)… Oh, and during school, I drive about 2 - 3 hours a day, in the summer, I drive about 1 hour. Highway miles, almost no traffic. And if anyone argues about the Fram DoubleGuard, no, I got no cites. Expensive = quality. Nuff said. –Tim ---
**Author:** ![voltaire](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/voltaire/32/313_2.png) [@voltaire](https://boards.straightdope.com/u/voltaire)\ **Post date:** [August 15, 2000, 4:01am UTC](https://boards.straightdope.com/t/motor-oil/29232/34 "2000-08-15T04:01:46Z")
> [@](#): > > -mrblue92 said: > Because your car uses outside air mixed with gas and burns > it. You are going to get dirt that the air filter misses and also from the partially unburnt fuel. Well if your engines seals are doing their jobs, the fuel, air, and incidental dirt should not intermingle with the oil. But once those seals are worn, all bets are off… ---
**Author:** ![Una\_Persson](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/una_persson/32/346_2.png) [@Una\_Persson](https://boards.straightdope.com/u/Una_Persson)\ **Post date:** [August 15, 2000, 4:35am UTC](https://boards.straightdope.com/t/motor-oil/29232/35 "2000-08-15T04:35:14Z")
> [@](#): > > \*Originally posted by Homer \* > \*\*And if anyone argues about the Fram DoubleGuard, no, I got no cites. Expensive = quality. Nuff said. > > –Tim \*\* Hey! That’s the same exact filter I used, until they stopped making it for the 98 Mustang GT for some reason. Nice choice! ---
**Author:** ![mrblue92](https://avatars.discourse-cdn.com/v4/letter/m/5daacb/32.png) [@mrblue92](https://boards.straightdope.com/u/mrblue92)\ **Post date:** [August 15, 2000, 12:19pm UTC](https://boards.straightdope.com/t/motor-oil/29232/36 "2000-08-15T12:19:29Z")
> [@](#): > > Well if your engines seals are doing their jobs, the fuel, air, and incidental dirt should not intermingle with the oil. But once those seals are worn, all bets are off… Hmm… I was under the impression that minute particles work their way in as the pistons move up and down. If the piston rings had a perfect seal, how would they move at all? There’s got to be a reason my oil gets dirty (even in a new vehicle), and that seems the most likely explanation. ---
**Author:** ![bump](https://avatars.discourse-cdn.com/v4/letter/b/7c8e57/32.png) [@bump](https://boards.straightdope.com/u/bump)\ **Post date:** [August 15, 2000, 1:09pm UTC](https://boards.straightdope.com/t/motor-oil/29232/37 "2000-08-15T13:09:31Z")
> [@](#): > > \*Originally posted by Yeah \* > \*\*I’ve been told that it was U.S. Air Force pollcy not to change the oil in some of its old prop planes (e.g., DC-3s); they just changed the filters regularly and topped off the oil. \*\* From what I understand, that’s perfectly fine, because for whatever reason(Anthracite- got any ideas?), aviation piston engine oil is straight mineral oil, so there’s not any additives to wear out. So as long as it’s kept filtered, there’s no reason to change it. ``` It's not the base oil itself that wears out- it's the viscosity improvers, pour point depressants, detergents, anti-wear compounds, ph buffers, etc... which eventually get depleted or wear out. ``` ---
**Author:** ![bump](https://avatars.discourse-cdn.com/v4/letter/b/7c8e57/32.png) [@bump](https://boards.straightdope.com/u/bump)\ **Post date:** [August 15, 2000, 1:16pm UTC](https://boards.straightdope.com/t/motor-oil/29232/38 "2000-08-15T13:16:49Z")
> [@](#): > > \*Originally posted by voltaire \* > \*\*Well if your engines seals are doing their jobs, the fuel, air, and incidental dirt should not intermingle with the oil. But once those seals are worn, all bets are off… \*\* Piston rings aren’t a perfect seal. You get unburnt fuel, water vapor, combustion end products, etc… blowing by, even in a modern engine in good condition. That’s what PCV(positive crankcase ventilation) is for- to ventilate that stuff out of the crankcase before it messes up your motor oil & creates sludge & other stuff. Plus, it helps on emissions control. Here’s a great URL about all sorts of car stuff: [http://www.autoweb.com/garage/encyclop/tocdoc.htm](http://www.autoweb.com/garage/encyclop/tocdoc.htm) [Previous page](https://boards.straightdope.com/t/motor-oil/29232.md?page=1)