19mpg in a Petrol... Believe it.

[BRE Fabrications LTD]

So I went for a bit of a drive today and considering I get crap mpg on LPG (10mpg) I figured I'd see what I can get out of my cruiser on the good stuff.

Distance driven: 127.2mi - Approx' 70% Motorway @ 60mph and 30%side roads/ country roads @ 30-50mph.
Tyres: 36psi
Fuel used: 28.92l std unleaded.
MPG: 19.9

WTF Ok, so I did baby the cruiser a bit, stuck under 2000rpm most of the time, only went over on the motorway. She does 60mph@approx 2100rpm, but surely driving style cannot account for an almost 50% gain in mpg??? I'll be the first to admit that I don't have the lightest foot around but I'm no hooligan either...

Wonder If I could have a leak on my LPG system somewhere, surely I'd smell it. Also I get roughly the same mileage out of each LPG tank so If i had a leak I'd think it would be a bit erratic.

Any ideas why I'd see such a big difference between LPG and petrol??

 

[J66P]

should be normally a 20% differnce, I say get the LPG set up correctly

 

[chadr]

My 3.4 V6 has consistently done 22-23mpg on motorway runs (@~65-70mph) when running on petrol ever since I've owned it - since 2004. Since the LPG conversion in 2009, the LPG consumption for similar runs is always around 17-18mpg.