Mick6186 wrote:Another advantage of the electric only pump is that it can be switched off to allow the engine to drain the float bowls. It takes a surprisingly long time. Plenty time enough to get out, open the garage doors and drive the car in. It might even clean the plugs!
I've not thought of using this for cars, but it's a necessary practice with "modern" fuel in the U.S. for small engines nowadays. If you don't drain the bowls and let the machine sit, the volatility will result in tar buildup on the floats and in the tiny passages that will cause fuel starvation. I've seen amazing amounts of buildup on mower and snowblower floats and started shutting off the fuel supply a couple of minutes before parking.
And a word about summer vs. winter fuels: In the U.S., the mixtures are different enough that my "other" car, a Prius V, drops from fuel economy in the mid 50's on summer fuel to as low as high 30's on winter fuel. Yes, the cold does lower efficiency a bit, but on the rare occasions I acquire a tank of summer fuel in winter, economy pops right back above 50mpg, so the formulation is the culprit. If you think about it, that's a pretty high price to pay for close to 6 months out of the year when the higher volatility either isn't really needed with modern ignitions, or if needed can be supplied the good old-fashioned way, by adding drygas. The cynic in me believes the formulation change isn't so much because it's needed as it is to give a boost to fuel sales during the months people drive fewer miles. Certainly the ecological impact of the drop in fuel economy can't be positive.