Oil type

Hello,
I was wondering what you guys thought/recommended regarding oil type? 72' GTO, 400 engine I have 10w30 in now. Should I go thicker? How about synthetic? Thanks in advance. Phil

If the engine is stock, or near-stock and in good shape, stick to the 10W-30.

IMO thicker oil is only recommended in engines that have been 'blueprinted' for performance, where bearing clearances have deliberately been made as loose as possible to reduce friction.

Thicker oil is also used as a temporary way to boost oil pressure in high mileage, worn-out engines that have very low pressure to begin with.

If your engine does not have the above two conditions, there is no point to using it. Frankly, thicker oil takes longer to start lubricating upon cold start-up, and increases stress on the oiling system.

Synthetic oil might cause leakage problems. I'm pretty sure your crankshaft uses rope-type oil seals, which are not as effective as neoprene seals. Sometimes, people have added synthetic oil in older engines (often with rope seals) then complained about a sudden appearance of new oil leaks.

Others may weigh in with different opinions on this leak issue. But IMO, unless you are driving the GTO a lot, stick with a good quality, name-brand conventional oil.

Thank you so much, very good advice. I'm dumping the 5w-30 today!

MR,

It all depends on where the car "lives". If it's in a hotter climate like Texas, Arizona or Southern Cal, 10W-40 is actually a better choice. Another thing to consider, with the Pontiac, the sheer size of the main journals calls for a little "heavier" oil. We send them "out" with 15W-40 Roetella in the.

As for synthetics, they WILL find a way out, if there's one available. They also, however, offer far better lubricity and endurance than conventional oils. Once the engine has been fully "broke in" and not leaking anywhere, our customers have been very happy with a 10W-30 or so, synthetic. They do say, it's hard to get used to 15 lbs. at a hot idle... Synthetic won't "carry" as much pressure at low speeds.

Jim

I would stay with the oil (Brand) that you have used in the past. If you are only driving the car during the warmer months you may consider a higher viscosity range, however be consistant and stay with the same brand.
No sense in creating potential problems.

MR,

It all depends on where the car "lives". If it's in a hotter climate like Texas, Arizona or Southern Cal, 10W-40 is actually a better choice. Another thing to consider, with the Pontiac, the sheer size of the main journals calls for a little "heavier" oil. We send them "out" with 15W-40 Roetella in the.

I did consider those factors, too. FWIW the original poster's location is NY state... nice and cool!!!

I use 15W-40 in my air-cooled motorcycle and industrial engines all the time as they seem to run hotter than the cars in the summer.

Also, a few years ago, I read in Car & Driver that 15W-40 (rated for diesel engine use) has a much greater percentage of a particularly effective anti-wear additive.

Gasoline-rated oils have much less or none of this additive because (if the car is burning a bit of oil) it is particularly effective at contaminating the catalyst material in a catalytic converter, thus rendering it less effective.

I also like using 10W-40 oil in higher-mileage engines in the summer. However, GM stopped recommending the use of 10W-40 oils about 20 years ago because the greater amount of viscosity-index improvers that they use leave too many engine deposits in the long run.

Who knows now, more modern oils may not have this problem. :)