I have an intermittantly noisy lifter (I think). I've been using Mobil 1 for the last70,000 miles (total of 150k) on my car, but in searching here have learned that lifter noise sometimes gets better with synthetics, sometimes gets worse.

Another thing I've learned from Duke and Larry Bible is that historically, oils intended for diesel engines have more detergents and thus can be used to clean lifters.

However, on some threads I've seen reference to diesel oils like Delo 400 being "the next best thing" to synthetics for cleaning the innards of a gas engine.

Just wondering -- between Mobil 1 and Delo 400, which actually does a better job of cleaning an engine?

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Steve
'93 400E