My vehicle is NOT an economy car. Its a 1 ton diesel dually. I use it to tow a 14k trailer at least once a month, and 1 or 2 week vacation. I can't afford another vehicle for regular driving, so I'm looking to increase my mpg. Towing, I get 9-11 MPG, and I'm fine with that. Other driving I'm getting about 15mpg. I started trying the stop start on lights I know I'll be sitting at least a half a minute and CEO on a .2 mile stretch and a .8 mile stretch. I am short shifting when I can without lugging, and have always tried to match lights so I don't stop. In 800 miles, 400 of it I've been doing this, my mileage computed manually is almost 21mpg. Does this sound normal, or did I mess up my calculations somehow?
Next question, how hard on my starter and batteries is this? And, is 10mpg driving once a month enough to clear out my EGR cooler?
Diesels use less fuel when idling than petrol, but its still worth switching off anyway. A typical small 4 cylinder petrol engine uses more fuel idling than it does to start it up after just 7 seconds, most people assume its a lot more. Starter motor and battery life may be shortened, no long term tests to prove anything as far as I know. Cars with stop start usually have beefier starters, I think it was Volvo tested theirs and detected wear after 175000 continuous starts. Do you have DPF filters? Slow urbanised journeys can clog them up with particulate matter, so be careful as they are very expensive to rectify.
Wayne Gerdes had to replace a starter on an Accord at the 3 year mark, but he engine offs every chance he gets.
Since you have a manual, try bump starting while engine off coasting(EOC is how I've seen it). That will prevent some starter wear.
21mpg does sound like a big jump; that's nearly a 50% increase. Plug in the numbers here to check.
The battery will see more wear. You could install a second one. A deep cycle one on an isolator could be wired to power the accessories while the engine is off. That is what people with those massive sound systems in their cars do, and GM did the same on the first Malibu with auto stop. Or just wire an identical starter battery in parallel with the first.
Thanks. To answer best I can, the increase was only 25%, not 50. I calculate towing and non towing separate. No DPF filters. I have that dreaded 6.0, but have the upgraded, "bulletproof" EGR cooler. It already has 2, 850cca batteries (both new and the starter is new). I don't have the monitor to show fuel consumption, but all Google searches says this engine burns .8 gals an hour idling.
Cash is really tight right now, but am looking forward to when I can fill up at least 2X in a row for more accurate results.
Guess for now, I'll keep on doing it until it either shears something out or the numbers show it's not worth the hassle.