Re: Oil Synthetic or Not? Gas - What Octane? With or Without Ethanol?

Posted by Rusty O\'Toole On 2009/3/5 18:55:35

Short answer: 10W30 and regular gas.

Long answer: Multigrade oils were new on the market when your car was made but all car makers recommended them as soon as they were available. 10W30 will be right for your car in any driving conditions you are likely to see. You might want lighter oil for below zero or heavier oil for above 100 degrees but I doubt you drive your Packard in such conditions.

Today some experts recommend using 15W40 Diesel oil because they have cheaped out on the high pressure additives in the gas engine oil. This is to reduce pollution on oil burning engines. Today's OHC engines do not need the high pressure additives like the old pushrod OHV engines did. In your case you have a flathead which is even easier on the valve mechanism than an OHC so you have nothing to worry about.

On the gas question, whatever engine you have, the octane should look like the compression ratio.Your engine with 8:1 compression would love 80 octane gas. Naturally this is not an exact rule, 87 octane regular will be perfect. There is no advantage to using hi test, quite the opposite. A low compression engine will run better on low octane gas. It will start easier, run smoother and cooler and develop more power and mileage on low octane.