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hello everyone,
my fathers 2003 yukon has 110,000 miles and for some reason it is only getting 15 mpg on the highway, it has a coldair intake and all maintance is up to date, it use to get 20 mpg. the only thing that has me worried is the trans, it shifts hard and makes some noise, could this be the root of the bad mpg? thank you very much.
Changed the fuel filter lately?
Plugged up cats maybe?
what's the weather like? Both my trucks lose 3-4 mpg when it's cold out...and I generally don't let them 'warm up'. Idle for 1-2 minutes for the oil to heat up, but that's about it.
15 mpg? That sounds great. I haven't got that in three years.
no it hasnt had the fuel filter replaced i will do that next weekend. Is there a way to check for plugged cats? the weather is mid 40s and low 50s, the yukon has always gotten 18-20 mpg no matter the season. And i keep telling my father to let it warm up , but he just fires it up and drives. any more ideas would be most appreciated. thanks again.
O2 sensors with alot of mileage get lazy and will give poor MPG's. But only the upstream sensors.
improperly inflated tires will decrease fuel mileage, too. If he's hauling more passengers or cargo than normal or heavier passengers it will cause a loss of mileage, too. Check the wear pattern on the tires, too. Alignment issues will rob MPG.
i went through the whole suv and everything looked fine, clean air filter, brand new tires inflated to the right pressure. the one thing i havent done is replace the fuel filter, how hard is that to do? thanks for all the help and advice.
not very hard at all. IIRC, the filter has quick disconnects at both ends. it sits at about the left rear door, just infront of the tank. another thing that can also cause poor mpgs is old plugs and wires. i need to do the fuel filter, plugs and wires on my 01, along with replacing my rims. but the rims will get changed next week