Whizzer Engine Oil
These oil conversations are always fascinating to me and end up leading to the same place religious and political discussions always do - nowhere. Depending on which forum you are reading people will insist to the death that you can not use detergent oil in a flathead ("they're old engines and detergent oils were not yet invented then"). Another contingent will insist you can only use petroleum based detergent oils in flathead ("you have to have detergents to suspend the carbon particles, synthetics foam, they're too thin, etc"). Yet another quarter will insist that you should only use synthetics due to their superior thermal stability ("in an engine that runs as hot as a free-air flathead you want the added thermal stability that only synthetics can provide"). I have my own oil biases, but that's not relevant here. The reality is that you can use any one of them successfully if you feel it is a good oil and change it often. The ability to keep oil in an engine with a poorly designed breather system is a separate issue. Fix the breather and use the oil you want if that's the issue.
I know many people that have used single weight and multi-weight synthetics in their Whizzers, Cushmans, Mustangs, and Harley Davidsons, and beat the living daylights out of them with absolutely no issues at all. I have personally used 0W-40 and 15W-40 synthetics in SV and OHV Whizzers, including for break-ins, with no issues whatsoever. Likewise, I know people that don't like synthetics or multi-weights and they fare fine too.
I categorically reject the contention that synthetic oils foam to the point of compromising performance in "normal" engines. If synthetic oil foaming were a real issue how would the Jap crotch rockets that turn 12,000-14,000 rpm and cruise at 8000 rpm ever survive if the oil frothed excessively? By comparison a 6000 rpm Whizzer engine is in slow motion. Which do you think is the tougher of the two applications on an oil?
Regarding oil aeration/foaming, what do you think the inside of a Whizzer engine looks like after running at 5000-6000 rpm for an extended period of time? I'll bet at that stage the oil sump is almost dry (because oil is being centrifugally thrown to the case surfaces and can't quickly return to the bottom end in the highly turbulent state), the oil is highly aerated, and the entire lower end is a wild mass of suspended oil mist/droplets driven by a rotating assembly generating turbulence akin to what sent Dorothy away in the Kansas twister. I think it's safe to say that all oils (petro and synthetic) froth appreciably under such conditions.
In cases where seals (or breathers) are not up to snuff, synthetics have always been more challenging to keep in an engine than petroleum oils. In engines with good seals (and breathers), both synthetics and petroleum based oils absolutely stay put.
On the subject of oil grade/viscosity, when oils are graded by the manufacturer, it is because they provide a specified range of viscosity. If the oil is graded as a 40 weight, it provides the same viscosity as other 40 wt oils. Synthetic- and petroleum-based oils of the same weight provide the same viscosity - synthetics are not lower viscosity.
Just my $0.02 worth. Please use the oil type of your choosing as there is not a right or wrong choice - only your choice.
