I think I might have been capable of making a 40mpg tank recently. Everything in the car was in working order (including the O2 sensor) and I was driving ~150 miles. Problem was I had no sleep for the first 75 miles so I was...not driving slow on I75/I4. This is only a VERY crude estimate but on the way back I must have been getting around 40mpgs because I believe I made out with about 35mpg INCLUDING my retarded sprint upstate. It's been a month or so since I made this trip so I don't remember any numbers but I am going to be back with a vengeance and some ridiculously good numbers sometime when I have had some sleep and need to make a long trip. Still stuck making I think only 26 or so mpgs in town but I'm thinking about lowering the idle (I set it a little over 800rpm back when I had some idle hunting problems), also need to get around to doing some electrical work including a battery gauge (you can bet I'll turn the car off more when I can see the battery charge status!)

 

I did an economy run competition last month and experimented with engine-off coasting. Didn't want to do it in the Yaris because it was too new or the BMW because it was too expensive... didn't want to replace the starter in either of them! But, in the beater Miata, I don't care. I can get a used starter for $20-30.

Anyway, I wired up a "kill switch" and stuck it (literally stuck it... with duct tape) next to the shifter so that I could pop the car into neutral and immediately kill the engine without having to reach for the key. The route was about 200 miles and was time-limited so that we averaged about 40 mph. (that doesn't mean we were able to cruise at 40... that included stops... so we were driving 50-60 where we could to make time) I was mostly pulsing up to anywhere between 50 and 65 and coasting down to 35-40 before restarting and accelerating back up to speed. This netted me about 48 mpg in my 1.6 Miata. I was hoping for 50, but didn't quite get it. (will next time because I've added a hard top and deleted the right side mirror)

Around town, I'm getting 32+ depending on how I drive. I took out my temporary kill switch. When I get around to putting one back in, I'll have the potential to easily get 40 mpg in the city.

 

Damn that's what you call hardcore. I want to wire up a killswitch to my injectors but keep the engine running off the transmission with the throttle wide open so I can just kick the injectors back on before the engine revs too low to recover, my wiring works sucks ass though so I'm definitely putting it off.

 

Yeah, it was kinda crazy, but it was an entertaining way to spend an evening! Who needs sleep?

 

Running a 600rpm idle these days.
Got the car weighed recently at the scrapyard (before and after 600lbs of scrap metal in the trunk!) the paper is in the car with the weight and my deductions for passenger weight (460lbs) and if I recall correctly the car is at 2760lbs with ~9 gallons of gas in the tank. This seems to mirror my claims as to approximately how much weight is missing from the car (600-700 lbs).
Gas mileage has been iffy (but still in the 20s)....I've gotten rid of the CEL (re-soldered O2 ground) and I've been running off my wideband but I'm thinking about going back to the NGK narrowband that I thought was bad.

 

Gas mileage discussion
ttt