I recently measured 42.8 mpg (or 5.5L/100km) with stricly highway. This was measured with 140km using 7.69Litres.

In the city around town it was recently 28mpg or 8.4L/100km with very short trips.

The valves haven't been re-aligned in over 7 years. It's a 1992 Civic DX hatch with 380,000km (238,000miles) on it. It currently leaks a bit of oil from the crankshaft seal (clutch side) and oil pan gasket with hard driving so I lay off the accelerator. I go no faster than 70mph (115km/h) while others wizz by in the SUV's, etc at 140km/h (88mph)!!!

Lately I added molyslip-e additive which promotes better friction. The molybedenum disulphide molecules form a lubricating layer between metal parts. Check it out on the bobistheoilguy.com (http://www.bobistheoilguy.com/moly.html).

I'm hoping for better gas mileage in the city after I re-align the valves soon (maybe this weekend). Can't wait to see the results of my work.

I'm surprised that some of you have such poor mileage on the highway.