WHAT OIL SHOULD I use in my Buick lesabre custom V6 conventional or synthetic


Asked by Apr 29, 2016 at 07:07 AM about the 2003 Buick LeSabre Custom

Question type: Maintenance & Repair

WHAT OIL SHOULD I use in my Buick lesabre custom V6  40,000 miles  on it .
conventional or synthetic . just concerned about a seal leak with synthetic  but
it is a better oil  ?

7 Answers


it should tell you on the oil tank


Check the chemistry all oil comes from the same sources, No such thing as Synthetic oil.. Really! speak with a real Petro Chemistry professor...During the refining process an addition chemical step is taken now it's called Synthetic oil. Use API or use whatever YOU think is best. Oh, a seal leaks or doesn't oils not the cause.Regards

1 out of 1 people think this is helpful.
Bob Beaman

I would run conventional to avoid seal seeping. Just change it regularly and use the recommended grade.

2 out of 2 people think this is helpful.

Interesting comments on the oils. That is one way to describe Synthetic oils, as Auto_Centric has described. Oils have come a long way and I believe either or in a good brand name are good oils. Synthetic oils are not a petroleum base oil as regular conventional oils, and are chemically made oils. They do have a tendency to find a weak spot in seals and seep threw. Thus seal softeners to add into the oil. Doesn't always work tho. I built a new motor for my truck and I am running it on Synthetic oil, and it leaks a tiny bit out of the front seal. I know the manufactures of new vehicles are sending them out the door with Synthetic oil in them now. Synthetic oils now blend with conventional oils, so you do not have to stick with it. On your vehicle and on most vehicles now a days run 5W30 oil. My motor is built up so I like running 10W30 Amsoil.

Bob Beaman

13 year old car with 40,000 miles might have sludge that synthetic may dissolve and disperse in my opinion using synthetic in this particular vehicle is asking for trouble. Also it might have been well maintained and have no sludge. Seal and gasket seepage caused from using synthetic oil could be significant in this vehicle especially the front and rear crankshaft seals. I will refrain from commenting on "Auto_Centric's"post regarding synthetic oil.

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Best Answer

Of course more to this subject, I agree with you there Bob, on an older motor cleanliness of the inside of the engine determines for me if to use Synthetic oil or not, I had tried it in my motor of 157,000 miles, big mistake. Thats why I built a new motor. I believe the motor should be pretty clean to use Synthetic oil over conventional. I just don't see anything wrong with using a convention oil for the life of a motor. Now a days I think it is a matter of choice.

2 out of 2 people think this is helpful.
Bob Beaman

I agree, Rowefast. I use Motorcraft Synthetic blend (it is mostly conventional oil) in my vehicles that are naturally aspirated, but I use full synthetic in my Ecoboost powered pickup that is turbo charged. Conventional oil that is changed per the manufacturer recommended interval or sooner will make today's engines last many miles.

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