Hi Volvo friends,

What kind of gas mileage should I expect from my B280 V6? The vehicle is a 1988 780 with almost 200k. I’m getting an average of about 18 mpg. I know the fuel tank overflow hose has a crack and leaks a little gas when filling the tank and allowing the pump to shut off automatically. I now try to avoid filling the tank. The idle also begins to go up and down between 700 and 2,000 rpm’s after idling for more than two minutes at a time (like at a drive through). Otherwise the engine runs great. I’ve checked for any vacuum hose leaks but didn’t find any.

Can one or both of these cause lower gas mileage? This is my first V6. I’ve owned four cylinder 740’s for years and typically get an average of over 22mpg.

Any suggestions? Is this typical mileage for a V6?

Thanks,
Michael
Melbourne, Fla

1985 740 460k (original motor)
1988 780 Coupe V6 190k
1989 780 Coupe V6 149k (parts car)
1992 745 197k