[Neil1314]

I noticed on a thread about fuel consumption that two people, both with P250 got really good mpg. Screen shot showing over 40 on a long run.
Now they both mentioned they were using the expensive petrol. We have never used this but I was wondering since our P250 returns about 31mpg if there is a case for buying the premium fuel.
Anyone done any comparisons on consumption with the cheap to expensive?

Neil

 

[Jph]

Hi Neil
My experience over the last 30 years and 7 cars is that in normal driving there is no difference in consumption between 94-98 octane fuel. I did see a an increase in consumption with 91 octane 10% ethanol mix in my ford falcon back in 2006-10 that meant it was cheaper per km to use the more expensive 95 grade fuel.

I find that the change in altitude between the beginning and end of the trip can make an enormous difference to the overall fuel economy and when you see these extraordinary figures quoted on the web you need to ask whether there was assistance from the down hill slope.

For example, When I drive south from Sydney I usually take a break after 150 kms where the altitude is about 600 metres higher than my start point. I just checked my last couple of trips and the economy figures are 8.0 litres/100km on the way up and 6.8 on the way back. Same average speed, fuel, tyre pressure and temperature . That's 35 mpg verses 41 mpg.

If you are going to be accelerating hard on winding up hill roads towing a caravan then use 98 octane so the ecu doesn't have to prevent pinging. Normal driving, save some money and use 95 octane.

Cheers
John

 

[Jph]

Btw
Those figures of 35 and 41 mpg were at an average 95 km/h and BP 94 octane 10% ethanol 😮

 

[alan969]

Premium fuels have more detergent added to keep the engine clean if you believe the marketing. I use RON 98 and Eco mode. MPG? Don't know, never checked but if there is some benefit by using premium fuels, all the better.

 

[rmj.]

I always use Shell Super 99 octane petrol. I've Just done a run from Brighton to Bristol in my P250 and it returned over 40mpg both ways. Going I used 'comfort' with the shifter set in auto Sport position (over to the left) and got 41.5mpg. On the return journey I used 'eco' with the shifter in D which returned slightly more at 43.3mpg. However the eco journey was not at all enjoyable, the car struggled up hills holding on to high gears unnecessarily and overtaking was very sluggish. Yes, I could have changed down myself but I wanted to compare both journeys in fully auto. I will never be using eco again, absolutely no pleasure driving it that way. The car has 7000 miles on it and is 18 months old. I hope this info helps?

 

[Jph]

Hi RMJ
Can you tell me what your avg speed was for each of the two legs?
Cheers
John

 

[Neil1314]

Hi RMJ Thanks for that, very interesting. We, I only get to drive occasionally it's wife's car, have never tried Eco didn't see the point.
Will certainly try Super if one can achieve those figures

Regards Neil

 

[rmj.]

John, these are the stats for my P250 Brighton-Bristol-Brighton trip recently. (Heavy rain reduced my speed on the outgoing journey and I had to make a detour on the return trip that added extra miles, but it was all motorway). Hope that helps.

 

[NGH]

I don't know if this will help, as the parameters don't match totally, but a couple of years ago I brimmed my wife's Mitsubishi ASX for her with ordinary BP diesel and noted the odometer reading. I waited the customary month for her to need another fill, leaving it until she was almost running on fumes (and was frantic), and this time, unknown to her, I brimmed it with BP Ultimate premium diesel. It was important for a fair mpg test that she didn't know she was driving a different fuel grade. Again, the car went down almost to fumes and I noted all the stats again. The ordinary diesel returned 47.2mpg. The premium returned 52.8mpg. The premium fuel was 8.4% dearer, but the mpg was 11.8% better. I know this is far from a scientific test, and that there were variables that were impossible to account for, although her driving routes were almost identical (commuting and shopping). I feel it shows that there is definitely something to higher-octane fuel. I'm sure it applies equally to petrol.

 

[rmj.]

Very interesting NGH, as you say there are lots of variables so it's best that interested people try it for themselves. I don't cover many miles so the extra fuel cost is negligible monthly, certainly compared to the vehicles depreciation! Once my tank is empty of Super fuel I'm going to fill with Standard and re-run the same routes as a comparison. Thanks for your informative input.