Should I use conventional or synthetic motor oil?

Question

I just got a 2000 Bonneville with 76000 miles. I don't know what type of oil is in it. I've been asking around and getting different opinions on wether or not I can use synthetic motor oil. Also, Is it possible to tell what type of oil is in it?

Answer 1

Bear with me. What I like to do with a "new" used car is look in the oil fill hole in the valve cover and also inside the throttle body to se how much sludge there is or is not on the rocker arms and in the intake manifold via the throttle body.

If the engine looks a bit dirty, dark deposits, then I'll change the oil and run it a month or two and then change it again. Those deposits will "wash" away when the clean oil hits it and two close together oil changes will help this process. Cleaning out the throttle body is a good idea, too.

As far as oils go, you can use either. The benefits of the synthetic is that is does not break down as fast and is actually slippery-er and you gain 5 horse power over a conventional oil.

It is very likely that your car uses a 5W30 oil. You can run any 10W30 or 10W40 in Summer and switch back to any 5W30 before Winter arrives. It is much easier for your engine to crank cold with a 5w30 oil in it. I like the store brand pure synthetics as they are cheaper than the name brand synthetics. You can also mix a synthetic with a conventional oil so you know exactly how many quarts of each are in the engine.

It has always bothered me that the semi-synthetics don't tell you how much synthetic oil is mixed with the conventional oil so legally it could be only 1% but they don't say. If you mix it yourself like two quarts of conventional to three quarts synthetic then you know your close to 50/50.

Oil is oil and just switching from one to the other is not going harm your car or make it fall apart.

Good Luck!

Answer 2

I'd just use conventional. I switched to synthetic once with a vehicle with about 85,000 on it and soon afterwards the head gasket started leaking and a wrist pin is ticking. From what I've heard, the extra detergents and stuff in the synthetic clean out some of the sludge thats actually holding things together. If the engine was brand new synthetic would be ok but not once its got some miles on it.

Answer 3

I used to test oil, grease, and antifreeze. I could probably look at it and tell you.

From my personal experience, high mileage vehicles do seem to do better with synthetic oil. Also, base your oil choice on the temperature of the season. During the summer months, I run higher grade 20w50 in my car as it is designed to work in higher ambient temperatures. Your engine oil really the primary engine coolant removing over 70% of the engines heat! The antifreeze/coolant only removes 20 to 25%. During the winter, I run 10w30. I live in a hot climate and this makes sense in my climate and it may not apply to yours. Also, this can be hard on the oil pump, but being as I know how I have maintained my car - this has been a non-issue.

As for brands (since I used to test the stuff), I prefer Mobil One or Castrol.

Answer 4

No there is no way of knowing unless there was a garage sticker somewhere.You can use synthetic oil but i would use one grade above than what is reccommended in the drivers hand book.You can look up the grade on the vehicle manufacturers website.

Answer 5

Use whatever oil you want to. Either one is fine as long as you change it freguently. Myself, I prefer the synthetic oil.

Answer 6

With that kind of milage i would stick with conventional oil.In a new vehicle i only use synthetic,as its break down point is out of sight......George

Answer 7

http://www.amsoil.com/redirect.cgi?zo=1463115&page=articlespr/articlemyths
informative article on different myths about synthetic oil