: : : I have a '49 WD that has never seen detergent oil. If I switch to Mobil1, what's the down side? So much crud breaks loose that it plugs passages, wears the engine out in 5 minutes, the synthetic finds every small leak in the seals and runs out, or should I expect to get away with this as long as I keep an eye on it and change oil when it looks bad? The lubrication is so much better with synthetic that I'd really like to change unless experience has shown that 'the cure is worse than the disease'.
: Keep the nondetergent oil in it until the engine hasw been majored,
: I agree, your engine remembers non-det. oil. Oils have advanced, tek-wise, but your engine hasn't.