oil for my car

Factual Questions
1

This is very likely a stupid question because I know almost nothing about cars. I apologize in advance.

I put a quart of oil in my car yesterday. It’s a '91 Acura Integra with over 250k miles on it, so it’s starting to burn oil a little more quickly than it used to. I put a quart in about once every month or two, plus I get the oil changed about every 3000 miles.

Yesterday, as usual, I looked on the shelf at the local gas station and saw a bunch of different kinds of oil. I always choose either 10w-30 or 10w-40, depending on which is closest to my hand.

What’s the difference? Is there one I should be choosing over the other depending on weather conditions, age/make of car, or something else I’m not thinking of? Should I actually be opting for one of those oils that starts with an S?

2

That would depend where you are. As the local guys what they use. Colder weather uses thinner oil, I guess.

No need to change at 3000 miles. 5000 miles is fine, we talked about this already.

Its not how many quarts per month, its how many quarts per thousand miles you use. Youre lucky that you have a car that was able to do that many miles.

3

It’s generally not a good idea to mix 10w-30 and 10w-40, but far more damage can occur if you let the crankcase get too low, so at least something is getting in there. I’m assuming you don’t have the manual handy which should mention the correct oil weight, but most cars in the 90s use 10w-30, 5w-30 or SAE 30, and have shunned the 40 weight. I’m no expert either but it has to do with viscosity levels and the heat generated by the engine. I would have the oil changed again and find out then what weight of oil is being used. Then always use that weight when you need an extra quart. The bigger issue is why the oil is being burned, but at 250K miles, it probably isn’t worth the expense to fix that as opposed to $1.25 per quart every month or so.

4

Look at your owners manual…if you can find it. It should reccomend what weight of oil to use in different temprature ranges. Use what the manufacturer reccomends. If you want to baby your engine use a good synthetic oil. I have had a lot of luck with Mobil 1, I used it in my car and it got me to 240,000 miles with no engine problems at all.

5

So is the 10-w40 more viscous? Or the other way around? Is it better to use more viscous oil in cold weather (which is what my instinct tells me)? What exactly does 10w-30 (or 40 or SAE) stand for? What happens if you do mix them?

I’ll see if I can find the owners manual…wish me luck. FTR, I used 10-w30 yesterday. Also, handy, since you mentioned weather, I live on the coast of South Carolina and it’s going up to 70 today.

6

::Multiple Triumph owner enters the room::

I know from oil.

viscosity. This is a measure of how thick (honey-like) the oil is. Lower numbers are thinner, higher numbers are thicker. Viscosity is temperature dependent; the higher the temperature, the thinner the oil gets. This works with oil being heated in a skillet.

Viscosity ratings. This is the 10W-30 or 5W-30, etc. This gives the range of viscocities. 10W-30, for example, gets as thin as a 10 and starts off thick as a 30. (Scale is relative)

What it means. In cold climates, you want to start with a thinner oil (like 5W-30). Your cold engine will have a tough time trying to turn over and mix a thick oil. In hot climates, you can deal with a thicker oil (10W-30). An oil too thin will pour down parts too quickly.

In South Carolina, it ain’t no big deal. 10W-30 or 10W-40 is pretty much fine. If your service station uses 10W-30 and you top it off with 10W-40, no oil police will show up at your door. Yes, you should use the recommended oil, but you don’t risk engine siezure or anything.

One thing you want to aviod is switching between detergent free and high detergent oils. This is usually not a problem, in that all xxW-yy and SAE oils have detergents in them.

Contrary to Handy’s post, I truly believe in the 3,000 mi oil changes, for two reasons. First, and of lesser importance (especially in your case), it helps with personal resale. Johnny Car-buyer will think twice about buying your car if you tell him you change oil every 5,000 mi. Second, in more metropolitan areas, there are gobs of things in the air that get into your engine and eventually into the oil (especially in the summer). These things (dusts not filtered out by air filter) can cause a lot of wear inside the cylinders. And heck, it ain’t that expensive to get an oil change.

7

sprittle said

But changing every 3000 miles rather than 5000 or more, as handy said, is a waste of time. As to whether you should do it because oil changes aren’t expensive, C3 would have spent about $1500. extra on oil changes during the life of the car. That ain’t chump change.

8

When I used to drive an old beater with a lot of miles on the engine, my auto-mechanic friends always suggested using the 40-weight instead of the 30, because the higher viscosity helped make up for the worn piston rings.

Now I don’t worry about it because I don’t drive crap (well, I do, but it’s new crap anyway).

First, let me recommend using the thicker oil.

Next, someone correct me if I’ve been ill-informed all these years. It makes sense, but that doesn’t really mean anything.

9

Anecdotal but also correct. Be sure to check with the manufacturer about using synthetics on an older car, as the likely worn seals can allow the syn oil to actually leak.

10

As I recall from many, many years ago working with natural and synthetic oils on a couple of different projects, I recall that a 5W30 oil would act as a 5 oil, and a 30 weight oil, its not really an “averaging”. In cold engines, the 5 oil lets the mechanical parts begin to move, but once the engine heats up, the 30 oil keeps it lubricated. At very high temperatures, all oil will start to break down and decompose its chemical makeup and thus lose its viscosity causing problems. Synthetic oils does not break down as easily, but they are much more expensive.

I still have cars from the 80’s, they leak. Since I add oil every few hundred miles, I don’t change the oil except every 5000 miles. The more important thing to change I think is the oil filter. I found some filters causing higher back pressure in fewer miles. You can watch this in the oil pressure gauge. Maybe the filter fibers swell up more or something. So I buy brands that does not do that. Because the engines leak oil, I also use the higher viscosity 10W40 in the summer rather than the 10W30 or 5W30 in winter. However, I also found that my '92 4 cylinder Subaru gets slightly worse mileage with 10W40 rather than 10W30, probably because this is a much tighter small engine, and it has a harder time pushing the higher viscosity oil around.

I would categorize a '91 Acura engine in the OP to be similar to the Subaru rather than the American engines of the '80s. Probably 10W30 will be better for gas mileage, although 10W40 will not hurt it much. 5W30 is not necessary in SC. Since it leaks, I would change oil and filter every 5000 miles. I also don’t think that mixing 10W30 and 10W40 will cause any problems. The only consideration (even if any) is the remote possibility of causing a problem by mixing different brands of oil that “may” have conflicting additives. I wouldn’t worry about it though.

11

If you can afford it synthetic oil would be my choice. Living here in the north it’s great to use an oil that doesn’t become tar like when it hits - 40C.

I would check your owner’s manual and use what the manufacturer recommends.

I strive to change the oil in our vehicles every 3000 km (2400 miles). This advice came from my father who was a master mechanic and changing your oil regularly really is the cheapest way to keep your engine running well for a long time. I was once helping my father do a valve job on the 400ci V8 in his '77 Newport. The car had 100,000 miles on it and while we had things taken apart we measured the cylinders for wear… they were within the factory specs for a new engine.

12

Changing your oil every 3,000 miles is a good idea–it protects your engine. I notice once my car gets to around 3,000 miles with regular oil, the oil starts to wear out - it doesn’t lubricate as well, and there is a noticable change in engine power.

I find with synthetic oil I can go about 1,000 miles further before it starts to wear out. Also, with the combination of a synthetic oil and a super lubricant like Dura-lube, I get an extra oomp in engine power (somewhere in the range of 5-8 more hpwr), relative to just using standard oil alone.

One thing that hasn’t been pointed out is the engine “tightness” when choosing oils. Most of the engines made today are pretty tight compared to the ones back in the '70s. If you have an older car, or a car with verrry high mileage, you’re probably best off with a thicker oil. If you have a newer car and you take good care of the engine you can go with a very thin oil. I use a synthetic 0W-30. :wink:

As for your '91 Acura Integra, 5W-30 is the factory recommended oil. However, since you say your engine is burning up oil, I’d stick with the 10W-30.

13

Wanted to clear things up a bit regarding viscosity of motor oil.

Basically, motor oil is a single weight low viscosity oil like 5-weight or 10-weight. If that’s all they were, their viscosity would quickly plummet as the temperature got higher.

So one of the major classes of additives are butylenes which are rubber-like molecules. When the oil gets hot, the butylenes make the oil viscosity increase. By varying the type and amount of butylenes in the base oil mixture, different viscosity limits can be attained.

The butylenes are the primary compounds that break down over time, causing loss of viscosity.

14

How do you figure that?
250K @ 5,000 per = 50 changes
250K @ 3,000 per = 83 changes
Net difference = 33 oil changes.

An oil change is $15, maybe $20. That’s $500-$650, not $1,500. So my question is, *Where are you getting your oil changes? * :slight_smile:

Also, 250K is way way above norm. How long do most people own their car? My WAG is 100K or less, which bring the difference in cost down considerably. For me, it’s more like 50K, which means the difference in cost is somewhere around $100-200. Especially considering how much better a 3,000 per rate looks to potential sellers, the cost difference is not very big.

15

You got me, muttrox I didn’t do my math right.

But you know what, when the guy towed my last car to the junk yard, it had 200K on it. And he never asked for my oil change record. :rolleyes: