Tach while cruising

I have an 86 with the 2.8L carb, much joy I must add. I travel to work with this everyday and notice my tach reads at about 3500 RPMs' while cruising on the highway. Does anyone else read around this value or is this too high? The carb was just completely rebuilt and might need to have the mixture rate readjusted, I say this because she gets about 15 mpg. Any ideas?

Another question, the oil pressure guage reads around 60-80, I could not find the limits in the shop book I have as to what they should be, any suggestions?

Thanks,

Hak

Your RPMs are higher than most of us see, but the 2.8L has more gear. Also, you didn't say what tire size you run or what speed you drive.

If you have 3.73 gears, your RPMs should be about 2200 RPM at 65 MPH in overdrive (if your tranny has overdrive), 3000 RPM if you don't have overdrive.

If you have 4.10 gears, it should be 2400 RPM/3300 RPM at 65 MPH.

Eagle are those rpms strictly for the 2.8 or all XJs with 3:73 gears?

All XJs with 3.73 gears and stock tires, give or take a few. The direct drive ratio for all XJ trannies is 1:1 (duh, "isn't that what direct drive means, teacher?"), but the overdrive ratio depending on tranny ranges from 0.79:1 to 0.72:1 so there will be minor differences there.

RPMs don't know what engine you have. 3.73 gears just means the drive shaft goes around 3.73 revolutions for each one revolution of the axle shaft.

Obviously, tires significantly larger than stock will move the vehicle farther on one revolution than a stock tire, which translates into "faster" for the same engine RPM. So if you're asking if those numbers also apply to a 4.0L running 38" Buckshot mudders, the answer is "No."