I haven't used MMO (mystery machine oil) to degunk my crankcase yet, my oil hasn't been changed in nearly 3200 miles, and I kinda dog it.
19 is the best fuel economy, 15 the worst (15 in the city in sweltering heat, stop and go traffic, and the engine was starting to get hot.)
To my surprise, after putting a new headgasket, head, valves, etc. on a 4.0L in a '98 project XJ I'm currently working on for a friend, the gas mileage now reads on the OHC as being far better than in my '96.
My '96 doesn't have an OHC, but calculated at the pump, I usually get 17mpg city and 20mpg highway. That motor has run on nothing but synthetic blend oil and is pampered like a baby. The '98 had been overheated several times before I got hold of it and the headgasket had finally blown; after cleaning up the mess and getting it back on the road, the OHC says it gets 20mpg city and 23 to 24mpg highway. The speedometer is accurate and both XJs are running on OEM-spec size tires, but I'll have to do an at-the-pump calculation at some point to see if this is true.
28-30mpg in everyday use and about 35-38 mpg on a longish journey (nowhere is that far in the UK!!) at 60-75mph. Best ever was 38.6 at a constant 50mph trying to prove that I could get 40 to the gallon out of it to a friend. Failed! I probably could now as I run higher tyre pressues these days! ................................oh did i mention it a 2.7CRD 5 cylinder diesel!!!
All quoted figures are measured tank top to tank top and not on the very optimistic overhead display!
Just as well.....fuel (Petrol or diesel) is over $10 a gallon over here so there is no way I could afford to run a petrol engined Grand.
95 Grand Cherokee, v8 5.2, I get around 11 in town, 13-15 highway. Most of my driving now is highway, but I am hoping to get that up a bit.
I think I need to replace the head gasket. I realize I am not goign to get really high mpg, but it would be nice to not have to fill up more than once a week. I have about a 70 mile round trip, mostly highway.
1995 Jeep Grand Cherokee ZJ
V8, 5.2 L