mlyon83

I'm taking a 2,850 cross-country trip. Does anyone happen to know the optimal speed for a '95 GCL 4.0L to save gas? Is it 55MPH?

Bustedback

Under 70mph works for me and my 95 ZJ 4.0.

mlyon83

Hey, BustedBack. It's good to still see you around. It's been a while.

Do you notice better mileage when you go under 55-65 versus 70? And how much mileage do you get in a full tank on the highway? I think I get about 350-375 miles.

Bustedback

The best mpg i ever got was 21, but that was with a good tail wind for most of the trip. 65mph works best for me, slow enough for good mileage, but fast enough that I don't see a bunch of middle fingers.

mlyon83

LOL!

Yes, yes... the middle fingers and honking of horns is priceless. Sometimes you have to wonder who is armed and who isn't when you're holding up traffic.

Thanks for the tips. I'll keep my trip at 60 - 65.

gasouthernxj

0 mph will save you the most gas

Michael952

indeed..

Turbocube

Legend has it that if an XJ goes faster than 100 MPH the turbulence created by its square rear is powerful enough to tear the fabric of space and time.

Pretty sure that's exactly what Steven Hawking is studying right now.

Derision

I usually hover around 60-65mph. I rarely hit 70+, and I think the best I've gotten is 18 miles per gallon. Not complaining.

motorcharge

Speed isn't so much a factor as RPMs. The more constant they are the better MPGs you're going to get at whatever speed.

Bustedback

Speed plays a major factor in fuel mileage. The wind resistance at 75mph is twice as much as it is at 55mph.

Michael952

100mph is a scary thought.
Mine would fly apart before I hit 95

highmileage

I believe that the part of the gas mileage formula is to stay in the middle to bottom of the torque curve(for us that would be 18 to2800rpm), at least that was what I learned on V-8s. The magic # for a V-8 with a carb is 62.8mph, least that's what the 1970s' how to tune your car book said.

oldschoolXJ

Best mileage I got was 8mpg. Lol so I just don't worry about it

Turbocube

My speedometer goes only to 85MPH and I'm pretty sure its calibrated wrong because when I pass one of those police radar stations that says how fast you are going it says 31 or 32 when my speedometer says 35.

At least its not reading too low, that would be bad.