hey!
I have a 2002 svt lightning.
Driving around town 50% and highway cruising at 50mph iam getting 9,6mpg !
Truc had a bad thermostat when i bought it, changed it out so now i get the coolant temp it should..any idea ? Its winter here so iam real soft on the throttle..
Is it normal ?
Iam from norway btw.

 

Getting that bad of gas mpg, something is off definitely.

When was the last time the fuel filter was changed?
When was the last time the intercooler was cleaned?
Do you have an oil seperator?
When was the last time you changed & regapped the sparked plugs?
What tune is on the truck, stock or aftermarket?
What mods have been done to the truck?
What octane gas are you using? (Hopefully no less than 91 octane from the pump)

 

OKI as long as he's running Euro 100 he should be fine as that's like 94 octane in the 'States

 

Stock truck.
milage on the truck is 51200.
Dont know when the plugs was changed.
So i should change the fuel filter and plugs..
no oil seperator, dont think the intercooler have been cleaned ever..
98 octane from the pump

 

Missed the last line that said he was in Norway

You don't have to change the fuel filter, but that is a simple thing to try but if the filter is clogged and needs changing, I don't think you would be having low gas mileage issues and would rather have truck not running right issues as its starved of gas.

No oil seperator, means that trucks intercooler is probably caked full of nastiness and if you are going to clean that you have to pull the supercharger off and you might as well pull the plugs to check them also, and change if necessary...probably best to go ahead and change them out. If I am not mistaken...having bad plugs and a nasty intercooler could affect your mpg.

If you pull the SC and clean the intercooler, then I would advise to install an oil seperator to help keep it clean. Get yourself an no maintanence one like L&S or D.M.R. (if you can find a D.M.R. as he stopped making them a lil while back)

The only other thing, that I can think of is that the previous owner had some mods done to the truck and then took them off when it was sold, but left the old tune tune on...you may want to see if someone near you has a programmer or can help you data-log to see what's going on to tell if its got the stock tune or not.

Lets see what some others say...like Tarajerame for some other suggestions.