Varying grades of lpg ?

Message

haynes_tm · #1 Post by **haynes_tm** » Wed Sep 20, 2006 9:54 pm

I'm recording my mpg at every fill up, and have recently had 3 figures considerably lower than the norm. My journeys are fairly consistent and I dont drive like a madman, so found it strange they were much lower than normal. Checking back on my receipts I realised these poor mpg's corresponded to previously filling up at a station I dont use that regularly. This station (BP) seems to have older pumps and I dont think is the normal Autogas used at shell where I usually fill up. Are there different grades/blends of lpg that could be affecting my mpg? Secondly when very nearly empty, the throttle response goes flat when trying to accelerate and only light throttle works - which I can understand, however I thought the system (OMVL Piro) would detect this and switch back to petrol, which it doesn't appear to and I have to manually switch back.

dmd · #2 Post by **dmd** » Wed Sep 20, 2006 10:35 pm

One possibility regarding your mpg is a variation in cut-off pressures between the filling stations you use. I have noticed that one filling station I have used consistently delivers more LPG to an empty tank than others. There are a few possible explanations, but as I haven't noticed a different mpg figure overall I am assuming that it is just filling my tank to a slightly higher pressure. To narrow this down, do you see an opposite blip on your mpg for the next tank after using this filling station? If so, then it might be a pressure variation. Also, what happens if you fill up at this filling station twice or three times consecutively? Do the figures come back to normal? I am not saying your theory is wrong, just suggesting other possibilities.

haynes_tm · #3 Post by **haynes_tm** » Wed Sep 20, 2006 11:26 pm

Hi Dave, I'm measuing my mpg based on the number of litres delivered from the pump. Even if the pumps were shutting off early, that shouldn't affect my mpg figures as I'm measuring the actual amount of fuel delivered - not assuming it does a full 80% fill. I haven't been completely empty filling up at this station (so can't confirm a full 49 litre fillup), so its possible the pump is over reading the amount of lpg delivered - which may be possible as it's an older type of pump with a mechanical counter. I'll have to go there completely empty and confirm if it is over-reading as from empty I know I get a shade under 49 litres (tank capacity 61 litres).

quantum · #4 Post by **quantum** » Thu Sep 21, 2006 12:12 am

Maybe I'm overly suspicious, but maybe the BP pump is cheating? In addition to overcharging?

brian_lee · #5 Post by **brian_lee** » Thu Sep 21, 2006 9:00 am

Welcome to rip-off UK, Bill.

andrew_kitcar · #6 Post by **andrew_kitcar** » Fri Sep 22, 2006 1:25 am

Hi, Surely the pumps at all filling stations have to be regularly calibrated as i`ve seen petrol and derv pumps done. Obviously it would need to be done in a different way but still needs to be calibrated.

brian_lee · #7 Post by **brian_lee** » Fri Sep 22, 2006 5:09 am

You'd think so wouldn't you? But then again you'd think the election of the most powerful man in the world would be based on the number of people who voted for him. Have a look at Fahrenheit 911.

bob · #8 Post by **bob** » Sat Sep 30, 2006 6:33 pm

Weigths and measures do check gas pumps. BP is a reputable company and they would not knowingly have pumps giving short measure. Giving short measure is seriously illegal. I do think that there are different types of autogas. I noticed that at A1 tool hire Poole Dorset the pump is labelled propane and that when I use this pump I get slightly less MPG than if I use BP in Poole. I asked the guys at A1 but they said the knew nothing about autogas and just take the money.