I use 15W50 which has, I believe, a red cap. I also agree with whoever
said that the taxi test probably wasn't the best test since taxi engines
run for long periods of time at relatively low loads. In this type of use
any modern oil would be sufficient. I would bet that, if enough miles had
been covered, the synthetic using engines would have been cleaner inside.
I read somewhere that Pennrite is marketing an oil for classic cars. I
don't quite understand this. The older engines, with their larger
clearances, need a heavier oil but modern oils are available thicker so I
can't imagine what the advantage would be. I suppose if you changed a car
from non detergent to the heavy detergent modern oils you could have some
trouble but otherwise, I would use the latest oil available. Few things
have improved in the last 30 years as much as oil.
BTW- the main driver for modern cars using thinner oil is fuel economy. If
you feel brave and want to improve fuel economy, try running thinner oil.
The car would run a little cooler as well. No guarantee on your rod
bearings surviving.
Regards,
Bill Eastman
61 MGA full of 15W50 Mobil 1or at least it was when it was stored.
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