Using Synthetic Oil in a Used Subaru

i purchased a 98 forester with 40,000 on it in 10/2000. have used synthetic (not blend ) ever since with no problems.

You could switch to Synthetic. But given you short mileage trips, you are not really going to benefit from the longer change interval. Do you really want to change every 3000 miles with expensive synthetic oil?!

From my understanding, the biggest risk of switching from a conventional oil to a full synthetic on an "older" car, is that where standard oils cause the seals to swell slightly, synthetic oils do not. This results in the potential for the seals to "unswell" and start to leak. I really wouldn't be too concerned on a one year old car with 28K, though. I've switched on cars that were older and had more mileage than that without any problems.

As far as the blends, they're said to offer most of the advantages of full synthetic for an appreciable savings.

However, for the short trips you're doing, I would tend to recommend a cheaper oil with more frequent changes. Short trips result in diluted oil that will eat away an engine, whereas longer trips burn off most of this dilution. I don't believe the synthetics offer much help in neutraulizing those acidic effects.

As far as the warranty, you should be fine with any of the above. Just be sure the oil you buy meets the weight and grade spec'd in the owners manual.

Jim M

I use syn oils in low mileage vehicles for an entirely different reason, cold starts. Since low mileage vehicles typically endure more cold starts per 1000 miles, I look it as cheap insurance.

You payz your money...

Hi,

I'm not sure, but I think the problems you've mentioned are ideas held over from the early days of synthetics. All of them for sale today have been modified many times over the years, as have seal materials, to the point I don't think there's a problem.

IF a switch to synthetics today results in increased oil leakage, I think it's a function more of the synthetic's superior cleaning qualities simply "opening up" areas that were sealed more by varnish and goo rather than the actual seals.

I switched my Subie to Mobil 1 for a "test" at around 250k miles--no increased leakage was noted. But it was already using about 1 qt/1500 miles on dino oil, and the consumption rate stayed the same, so the economics of the situation said "use dino!" OTOH, I switched my Camry ('92 V-6, with the "usual" tiny leaks that engine's noted for) from dino oil to synthetic blend at 225k miles: the leaks are hardly noticeable now, and consumption went from approx 1 qt/2500 miles on dino to approx

1 qt/5000 miles on the blend. So I wouldn't worry about leaks!

Rick

I have used synthetics in all my cars since my wife coked up a 86 Chrylser

the only downer is that it is really easy to get a really dead battery since the engine cranks so easily and quickly year-round that a weak battery is easily over-looked.

That's true. I had a Saab 900 turbo and put in Mobil 1 when the car had

147,000 miles on it. That was a mistake. It blew out the main seals. Lots of oil loss! Then I confessed to my mechanic what I did, and he said he never uses synthetic.

Tom

Hi,

I'm not surprised... this kind of problem's often reported, but I don't think it was so much that Mobil 1 "blew out" the seals so much as it "cleaned" whatever goo was holding the engine together out, and then started leaking. Being a turbo with that kind of miles, I wouldn't be surprised at a fair buildup of varnish created by the extra heat. And... if they were the original seals, they'd probably already lived a pretty good life, again just cuz of heat. Leaks between 60-80k miles aren't uncommon as seals get hard and crack--seems to affect many makes.

I know it's too late now, but I'd have been curious to see how that same engine would act with all new seals and Mobil 1...

Rick

Yeah, but I wasn't interested in trying it. It probably would have been just fine, but why go through an extra cost while going against my mechanic's advice?

So my 2000 Legacy wagon has 54,000 miles on it. Seems like a good time to switch, huh? No turbo, of course.

Tom