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oil and brake fluid for 1994 Pontiac Trans Sport

Hello!

I have a question about oil grades and brake fluids. The manual for my

1994 Pontiac Trans Sport specifies that an oil like 5W30 or similar (all ending in 30) must be used, and that the brake fluid should be DOT3. But the workshop at the local dealer's (there's only one where I live, Canarys islands, Spain) says that 5W40 is just great, and that DOT4 brake fluid is "just like DOT3 but improved". It seems odd to me that the manual (and caps on the car) should insist on the other numbers. Can anyone give me an opinion? Is there much difference between DOT3 and DOT4? Does it not matter if the oil is thicker?

Thanks for any help!

Marianne

P.S. Apologies if this comes through twice.

Reply to
Marianne Perdomo Leonor
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Where you are, in the Canary Islands, you sure don't need the 5W rating, as you do not get below freezing temps, and 40 or 50 weight is great for high temps. I would use 15W40 or 20W50 without thinking twice. (I've had "tropical" experience in central Africa) As for the brake fluid, definitely use DOT4. It has a higher boiling point and a few other "improvements" over DOT3. Do a complete flush and replacement to get the maximum advantage.

Some "experts" will warn against wide spread oils like 10W40, stating there are too many "long chain Polymers" in the viscosity improvers, that break down causing viscosity breakdown. In my experience that is only a problem with today's oils if you extend the drain interval too far. Change oil 4 times a year, maximum 8000 miles, preferred 5000, and the "problem" will never occur, assuming you are using premium quality motor oils. (Agip, Shell, Mobil, etc)

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