Best oil for Roadmaster Wagon LT1?

[larkwagon]

I have a 1994 Roadmaster Wagon. 174,000 miles. Had 168,000 when I bought it. Oil had been changed every 3000 miles at a quick oil change shop. Windshield sticker said Quaker State 10W30 is what they were using.

I changed the oil and put Castrol 10W30 for high mileage engines (from WalMart). What should I be using? What is the best (non-synthetic) oil. After an internet search, I am afraid if I switch to a synthetic, my seals will start leaking. Is that a valid fear?

I will cahnge oil this weekend.

 

[Rickey]

I personally don't know of any issues with changing to synthetic regarding high mileage including seals. I have a '96 Caprice with about 175 thousand on it. This car has the L99 engine in it. It has had synthetic in it from 24 thousand, mostly Rotella T 5W40 from Wal Mart. It did develop a small leak around the oil filter adapter at around 100 thousand. A new O-ring fixed that. My opinion is that these older tech V8's prefer a slightly thicker oil. Maybe a 10W30 summer and 5W30 winter for a conventional oil. If you do dare to try a synthetic a 5W40 would do nicely I think. I have my own personal preferences regarding brand, but I really think any of the "name brand" oils will serve you well. I do think the Purolater Pure One filters do a superior job of keeping the oil clean longer. Just my 2 cents. Good luck. Rickey

 

[Al]

Well the new specification for oils is GF-4/SM . Since this has come out none of us knows which oils are going to be the "best". I feel though all of them will be better and many cases rival the full synthetic. You almost can't go wrong. MotorCraft, Pennzoil, Castrol, Hovoline, Chevron have all put up good numbers in the past.

Mobil 1, Royal Purple, Redline, and Amsoil are the really only "True" synthetics and your engine would be unlikely to leak from them. But your vehicle has been doing great on conventional oils.

 

[JHZR2]

your engine has been doing gret on (bulk) standard conventional Quaker State oil. You dont say that there are any leaks yet, and want to ensure that none start up. Valid concern.

If there are no leaks, IMO, High Mileage oils are not a good choice. id want minimal artificial seal swelling, and those High Mileage oils have artificial seal swellers in them to band-aid up leaks that may have formed.

For that engine, Ill bet that pennzoil 5 or 10w30 would be a great choice. Havoline would be my second choice.

Other good options would be shell rotella synthetic 5w-40 (great bang for the buck), or if you want a true full syn, Id say to try Mobil 1 10w30 or maybe better yet 0w-40. If you think that the engine is particularly dirty inside from years of conventional oil use, Id suggest using M1 truck&SUV for a number of changes at least.

You might consider using auto-rx, per the instructions, with either the pennzoil or havoline. You could probably actually put it in (replace the filter when doing this) after you have about 1000-1500 miles on the oil currently in there (High Mileage oils do have some synthetic component, but its usually very small), then do two flushes or so with pennzoil/havoline, and then either keep using the same or move to one of the synthetics.

Given that you don't know the engine's history that well, Id say that the auto-rx, or at least a change or two with a diesel-spec oil (rotella syn would be my first choice, but Mobil 1 Truck and SUV which is expensive, or chevron delo 400/mobil delvac 1300s would also work, though IMO a bit thick).

JMH