My father-in-law drives a Toyota 4Runner. Whenever I’ve been riding with him and we need to stop for just a few seconds (ex. running into the house to grab a jacket), he turns the engine off. He says he does it “to save gas”. I believe that he’s using more gas when he starts it back up again, but he disagrees.
Any opinions?
Sorry, he’s more right than you, but the difference certainly is worth worrying about. And with the potential for ‘a few seconds’ to turn into a few minutes, he’s definitely doing the right (and safe) thing.
The cost savings in gas will be negated when the starter becomes worn out and requires replacement.
Tester
Disagree with Father-in-Law
“Any opinions?”
Yes, it’s not a good idea to disagree with your Father-in-law.
Are you nuts?
Normally, I’d agree, but OP’s example was for situations where he’s getting out of the car. Major safety issue there, should always turn off the car and take the keys when he gets out.
Sorry, I didn’t explain that clearly. It would be ME, the passenger, getting out. He stays in the car.
And by “a few seconds”, I mean literally 10-20 seconds.
OK. Does he do this at stop lights? If not, then it’s really not worth the discussion. If you’re gone for more than 30 seconds he’s definitely saving a small amount of gas, and wearing out (very slightly) his starter.
Good point about the stop lights.
Definitely a tiny amount of gas lost. I was just curious. Thanks for your input!
Back in the bad old days of carburetors you would be correct, but modern fuel injection means it takes very little or no extra fuel to restart a warmed up engine. So, turning it off if waiting more than 10 or 20 seconds almost certainly saves a tiny amount of fuel. I’ve never worried too much about starter life. Again, with a warmed up engine the load on the starter is pretty minimal.
Here’s how to get some points with the FIL - if his 4Runner ever starts to have intermittant starting problems (good battery, but engine doesn’t turn over until he tries several times), tell him all he needs to do is replace the solenoid contacts and disc, about $30 (if he does it) compared to $200 for a starter. Toyotas often do that at some point (about 8 or so years). Just don’t tell him it was because of his frequent starts!
Perfect! He loves a cheap, er, “cost-effective” fix 
Thanks! That’s good to know… even if I was wrong 
I think he may be saving a little possibly. If my figures are close, he may be saving a couple of tablespoons of fuel for a 30 second stop. The savings isn’t exactly going to pay for lunch.