I'm considering an x308 and have the choice of plenty of 3.2 models and a few 4.0 - and I'm leaning towards the 4.0 as I understand it has more relaxed gearing thanks to the higher torque.

I wonder whether anyone has stats on the cruising rpm at 70mph for either/each please?

 

I recently replaced my 3.2 with one of the supercharged 4.0 models. I didn't keep stats but there's no difference in ability to cruise at motorway speeds - you just get there more quickly 😉

The 3.2 can feel a little underpowered, however, so all other things being equal, I'd choose a 4.0.

 

Did the 3.2 models come with a 3.27 diff ratio vs the 4.0 has a 3.07? What I’m getting at is if in fact the 3.2 has a 3.27 ratio, at 70 mph your cruising rpm will be higher but the smaller displacement will be fuel savings so it might be a wash. Anyone else have any insight on the diff ratio on the 3.2? I wouldn’t know where to look to verify the diff ratios on the X308 3.2.

 

2001 XJR, no modifications. At a steady 70 mph my tach s showing just shy of 2500rpm...call it 2450-ish?

 

3.2 came with 3.27; 4.0 with 3.06, except Mexico. At a steady 70, the tach will read higher on the 3.27