I've got a 98 GS400 with Nav. Had it for a little over a year. Since I first got the car, I was getting between 19-21 mpg (according to the trip computer). Now, I drive like a grandpa, no burnouts, and fairly consistent speed.

This past month, that statistic has dropped to 13.5-15 mpg. I was very surprised, as my driving style hasn't changed at all. I do take more local streets than freeway miles now, but is that a 5 or 6 mpg difference?

Any ideas what I should look into? The tires seem to be inflated properly, but I don't have a pressure gauge on me to be sure. thanks in advance.

 

Besides airing up the tires.....get a wheel alignment....check the spark plugs (maybe time to change it)....clean the air intake filter....change oil....swap out trans oil...etc....

You can also try some gas cleaners, fuel injection cleaners, etc....

Do you use the A/C often? More than usual now since its the summer? That's another reason it could have gone down.

Good luck.

Pete

 

Thanks for the quick reply Pete. I'mll give those suggestions a try, and see what happens. OTOH, is 15 mpg normal for the GS400? It may not be that out of whack.

 

I ge t 18-20 mpg when I drive 80% freeway 20% city. But when I drive 10% freeway and 90% city I get 15-16 mpg.

 

Don' t have a trip computer so I really on dividing miles per tank by gallons to fill. I average about 15-16 mpg in mostly city driving. I have never gotten 19-21 mpg (based on a full tank).

Have you ever calibrated your trip computer (compare manual calculations to the computer calculations)?