MPG on the trip

i have a 99 montana EXT. We took the family vacation which is 600 miles 1 way. removed the rear seats so we could get everything piled in. had the kids in the captain chairs. I replaced the air filter and fuel filter. I averaged about 26-27 mpg on the way there. On the way back it was a different story. For a while we we stuck behind slow cars going 50-60mpg, at that time i was averaging 34mpg as the Driver Info Center showed which was shocking since i never saw it that high. but as soon as we hit the interstate going 80 the MPG dropped down to 23. anyone have similar stats?

I just took a 3000 mile trip, and we averaged about 22-24 with 4 people and averaging about 70 MPH while on the highway. I wouldn't trust the accuracy of the DIC as far as MPG since it is just using a map or table in the computer to estimate the fuel consumption based on an assumed fuel pressure and injector pulse width. I check my mileage with every tank, and I find that the DIC is about 0.5-1.0 higher on it's MPG estimate than my calculations based gallons required to re-fill the tank. I know there is variability in my ability to fill the tank to the same point each fill-up, but over time that would average out. So, I think I can trust my 22-24 MPG numbers.

By the way, were you looking at instantaneaous or average MPG?

Take care, Glen

50-60mph is more a "sweet spot" then 70 or 80mph. That would lead to better fuel economy. Also, if the wind was in your favor and you were drafting the driver in front of you, that would give you an additional boost. 34MPG is a little more then would be expected though.

My DIC miles per gallon is ususally off by about 2 mpg (estimates too high). I can get on road trips 23-25 mpg at best and ususally 18 in town. Once again it seems to be consistenly 2 mpg off in city driving or highway, I guess this thing cannot be calibrated? I have seen my overhead get up to 31 mpg, but after an entire tank the real numbers are not near that.

yeah i have never got 35mpg on the dic and yes i always have it on 'AVG MPG' not 'instant'. One year i filled up in Montgomery, AL and got home(southern Indiana) with 1/4 tank left so i was doing pretty good. But it takes a good wallet to filler up.

I will say, I do like the large fuel tank. We drove over 550 miles on one tank during one leg, and it's nice not having to stop as often.

mhall2, I think I get almost exactly the same MPG as you do....Glen

yeah i have never got 35mpg on the dic and yes i always have it on 'AVG MPG' not 'instant'. One year i filled up in Montgomery, AL and got home(southern Indiana) with 1/4 tank left so i was doing pretty good. But it takes a good wallet to filler up.

I can't say that the overhead system (DIS) is totally accurate, but we did travel through the Rockies and back in 2002. Drove from Toronto to Victoria, BC (OK, we cheated and took the ferry across from the mainland to Vancouver Island!).

Averaged about 33 miles per Imperial gallon (4.55 liters) with a full load (rear seats still in, luggage for two adults and two teens).
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We took a 700 mile trip in our 99 Montana with seven people and a car top carrier bag. We averaged about 27 mpg. I like that mileage.

I generally peg my cruise control right at the speed limit, so I usually go about 65. When we go on vacation, I usually get about 27 mpg according to the computer. If that's actually 25, I'll still take it!

I'm looking forward to checking it on this year's vacation in a couple of weeks, because I just replaced plugs, wires, filters, etc.

The large tank is a real plus. A couple of years ago, I drove all the way from Northeast Ohio to Myrtle Beach, SC on one tank. OK, when we were about 25 miles from MB, my wife kept begging me to get gas, but I had to be able to tell people I made it on one tank! We did it, but it got a little scary at the end!

I average 19-20 in mixed driving, and on my last trip (70MPH with few hills), I got about 28MPG, which is a little higher than I am used to (usually about 24-26).

flatland driving, no A/C, and with TC off, I get 32 mpg when 55-60 on highway. New air filter seems to help, too.

CAUTION: I got 35mpg once but a smog system check for annual license plate renewal failed as "too lean". What was happening was one injector was fouled with a speck of something and its rich mix in the exhaust caused the system to run very lean. After an expensive replacement of all the injectors, I keep the fuel filter replaced regularly and sometimes throw a jug of injector cleaner in the tank when the tank is running close to empty. The fuel filter can is under the driver's side and is easy/cheap to replace.