Oil use question

[TMA62]

I have a 1971 Avanti II. The engine, a GM 350, had 145K miles on it before the engine was rebuilt last year. It has now about 3K miles since the rebuild. The oil was changed about 2.5K miles ago. Presently, I have 15W40 oil (Rotella) in it but am thinking of putting 10W30 since we are approaching winter. I live in central Indiana and we do get cold winters. I will plan on driving the car sparingly during the winter only during good weather and dry road conditions. The car is garaged.

Given the above, what are your thoughts? What do you use in those 327's and 350's in winter and summer?

Thanks in advance!

[Gunslinger]

I use 10w-30 in my '70 year round. What you're doing is perfectly fine. Regular oil and filter changes is more important I believe.

[IndyJimW]

I'd recommend GM's Dexos 5W30 year round. The 5W makes for easy winter starts and the 30 is good for our summers. Being a semi-synthetic at a good price makes it a win-win.

[Devildog]

Rotella, DELO, etc. any of the oils that have a CJ or CI rating in the API logo. These are rated for diesel engines. The CJ/CI oils have 800-1200 ppm of ZDDP (zinc phosphate) compounds which is an extreme pressure additive.

This is required to reduce wear between the cam lobes and lifter base where great pressure exist in these older style 'flat tappet' valve trains.

Not a concern in most of the engines produced in the past 20 years which have 'roller hydraulic' valve trains.

Joe

Edited October 6, 2013 by Devildog