Car Experts - Synthetic or Regular Motor Oil?

It's that time, what would you place in a 2L 4 CYL Turbo engine with just over 100k miles on it?

to keep it on what it is used to. His humble opinion is stick with the regular. He had a 78 Chevy Caprice (gratefully glad here that it's dead now) that he tried the synthetic on and he reported a difference in performance. He only puts synthetic in the new one though, and would never therefore put regular in it.

that's what I'm currently doing with my GTP. Go two or three oil changes with the durablend before going full synth.

I heard synthetic is a thinnier liquid and thus is more likely to leak out of older engines (like you 100k). If I were you I would find oils made for older engines instead of synthetics.

It's thinner as low temperature but undergoes a far lesser amount of a rheometric phenomenon known as "shear thinning". So, in the engine itself, it stays at the proper vicosity despite the high shear forces of piston against cylinder.

At room temperature, its viscosity is lower, and it has a similar rheology v. temperature curve. But, because of it's lesser nonnewtonian behavior, it's ok when the engine is actually running.

The detergent content is almost exactly the same in both synth and petroluem oils. So, the ability to micellize carbonaceous matter is the same. It's breakdown temperature is much higher so it last longer.

However, i've never seen any studies that indicate that it actually extends engine life. It might, but i've never seen any such data.
The Professor

Synthetic, without a doubt. With a higher mileage car like yours, you may experience some oil usage and even some oil leakage where none has occured before. The reason is that the oil molecules in synthetic are much smaller than normal oil molecules. While you are at it, use synthetic in your transmission. Red Line works well in manuals. I have a 1991 Acura (with an automatic) and use Honda fluid in the transmission. It was a big improvement over Valvoline.

Try a synthetic blend oil, which is a mixture of synthetic and mineral-based oil. I use this in my car, it provides higher oil pressures and stands up well in the Florida heat. This oil is also supposed to be more environmentally-friendly (if any motor oil could ever be considered as such).

Most synthetic blend oils are usually 5W-20 viscosity. Don't go with a straight synthetic, unless that is what you are already using.

One more tip, if you replace the oil yourself, before starting the engine, disable the ignition (or fuel system) and crank the engine until the oil light goes out or the oil gauge reads pressure. This will help extend the life of your turbo, as it will not be deprived of oil.

I switched over from 10W-30 Pennzoil to synthetic in my BMW 2002 4 cyl engine with 55K miles on it. Bad move. During the engine rebuild they found all my main bearings scorched.

Evidently, the synthetic does a great job of dissolving the oil deposit buildup on an old engine, which in turn gummed up the lubrication pathways to the main bearings, one of which seized and parted the connecting rod. There were piston pieces everywhere.

So my synthetic oil switchover experiment cost $2500.

I've had both a boss and a friend blow the engines in their BMW's after switching from regular to synth. Maybe there's something in the BMW engine that just doesn't like synth?

I'm in Virginia, and I run Mobil One 15-50 year 'round in my Bimmers. I have an '88 735i (five-speed, very rare!), a '87 325 and a '73 2002tii (each with at least 150K). Have had no problems whatsoever, and have been running Mobil One in them since the early '90s (each one got an oil change with the synth juice on the day I bought it).

mikey_the_rat

In fact, the M5 (drool!) comes with an extra quart in the trunk because they know the engine will burn off that much in the first 200 miles. Germans and their damn tolerances :evilgrin:

My Honda Accord 1992 has had Mobil 1 synthetic in it since I bought it back in 1992 and I am about to roll over 200,000 miles on it.

is stick to what you have been running.
if you really want to make a change go for a blended oil.

The upsides to synthetic oil are longer engine life, easier starts, cooler running, better mileage, reduced emissions, and smoother idles. The downsides are a slightly incresed chance of oil leaks or oil burning.

If your car leaks oil or smokes AT ALL, stick with normal oil. If your car is well maintained and in good running order, switch to synth. Even higher mileage cars will benefit from the reduced wear and friction. My 1999 Mazda with 92,000 miles has run synth since about the 50,000 mile mark. When I had my first smog test a few weeks back, the tech walked into the waiting room and commented "You must run synthetic in that thing". When I asked him how he knew, he commented that it "smogged like a car with half its miles". Not bad! :)

Synthetic, Petroleum, or stick with what I'm using now. Problem is, I don't know what's been put in last, but it's probably petroleum. I'll look into a durablend also, and consult the DSM forums on the net.

Thanks everyone! There's been some good advice here!

Esp with 100K Every car at that mileage has leaks. Synthetic stays viscous. Cheap insurance. Used it in my Bmw ..use it in my mustang and used it in my porsche (now dead and buried thanks to the tree that got in my way that night)

nothing but conflicting opinions on this thread, not that I value yours, or anyone else's, any less.

At this point, I think I'll call the last dealer I sent my car to and find out what was used last, and use that again.

If I had more money to put into the car, I'd replace a lot of stuff, and add this and that (hell, after 100k miles, I'm still on the original shocks, so shoot me), and get a good 500 whp out of it. But money lacks, perhaps Bennifer will be filming one day near me, and J Lo will choke on a MA grinder, and I'll leap into action and give her the old heimlich manuever, and Ben will give me the car of my lowly dreams (98 Toyota Supra Twin Turbo Six Speed Black Custom Wheels, no smokers). One can dream. Hell, it'll cost him less than a toilet seat.

Although I use synthetics in our two newer cars, I would not recommend a changeover to the synthetics at 100k miles. You may well unleash built-up material into the turbo by doing so.

I suggest a turbo-rated 'high mileage' traditional oil such as Valvoline.

I ran a Suburu Legacy for its first 100k on Pennzoil, then switched to Valvoline high-mileage for another 50k. The car did not use a drop of oil at 150k when I sold it. I am also convinced that the engine ran even smoother with the hi-mi oil.