Vintage Cars: Oil Viscosity for 1964 Bonnneville, shell rotella t, oil viscosity

Question
Hello,

I recently purchased a 1964 Bonneville convertible with 73,000 original miles on the 389 cu in engine. The car runs perfectly, and does not burn oil or smoke.  I am due to change the oil, and I am unsure of the proper viscosity.  Should I use a multi or straight weight oil?  Is any brand noticeably better than another?  Someone told me I should use 30 weight Shell Rotella T due to the additives that it contains.

Thank you.

Vince

Answer
Shell Rotella is a good oil, but it isn't that much different from a lot of other quality oils.

You can run synthetic in it, and I would stick with a 10-30 or 10-40 oil.  If you don't drive it in cold weather, a straight 30 weight is also OK.  If you DO drive it in weather near freezing, then switch to 10-30.

There are all kinds of oils out there now that say they are for "older" engines.  They would have you believe that you need them no matter what.  Truth is, you don't want to use that kind of oil (I use Valvoline MAXlife in one of my older cars that had a few minor seal leaks and it helped) unless you have a leaking problem.  THose oils won't do anything for oil use through rings or valve guides, but may help with a tiny leak at the crank seals or similar.  If you have a big leak, they won't help much at all.

So if your car is not leaking, and not smoking or burning oil, use a regular oil or quality synthetic (Amsoil, Mobil 1 are both excellent).  There is no truth to the old mechanics tale that synthetics will cause leaks in older cars.  If anything, they will reduce leaks because they won't thin out like regular oil when hot.

Stay away from 50 weight "racing" oil and don't use things like STP or other additives.  Just a good quality oil and good filter, and change it once a year in the fall if you drive less than say 1500 miles a year.  If you taka a lot of short trips, and put on closer to 3000+ miles, then change it twice a year.  If you put on a lot of miles, then change it every 3000 miles.

The once a year thing for cars not driven much is valid.  change in the fall if you put the car away for the winter.  Then don't start the car every month or so as some people will recommend.  on my old cars I won't start them unless I can drive them at least 10 miles and get things fully warmed up.  Starting an engine and letting it idle for a few minutes a month is death on exhaust systems and puts moisture in the engine from condensation because the engine and exhaust never get up to full temperature.  BEtter to let the engine sit for 6 months and start it up and drive away in the spring.

Of course if you drive it year round, then just follow the 3000 mile advice or sooner.  

For daily driven cars with a good synthetic, you can extend oil changes to 7000 to 10,000 miles in most cases with zero concerns.  But older cars, heck, change it a little more often and don't worry.

Of the oils I like I like Amsoil synthetic, Mobil 1 synthetic, Valvoline regular and synthetic.  My dad used to run nothing but Wolf's Head in his Pontiacs in the 50's and 60's and you can still get it.  I am NOT a fan of Pennzoil.

Don