26.9 mpg?????

[Moosey]

Hi all,
Yesterday I had to drive a 500 mile round trip to the DVLA in Swansea.
(Had to exchange my old Irish license for a UK one - I know you can do this by post but my work will not allow that)
After the first fill my predicted range said 307 like it usually does and off I went.
M11,M25,M4. Honestly thought I was going to have to fill up again before I got there.
Imagine my surprise when I made it there and 45 miles back before I decided to pull in at a Shell garage (and not risk one for the further 40 miles range I had left)
So that was 255miles done at 26.9 with plenty left!

I only say I'm surprised as the only other long run I've done so far was driving it home from Lincoln after I bought it and that only provided 22mpg on a sedate drive with only one heavy footed moment.

All I can attribute it to is me running it on V-power versus the dealer filling it up with BP 95 octane for that first trip.

Anyone else noted vastly differing MPG when using less than 98 octane?

 

[DavidL]

I would tend to expect better mpg on 98 than 95 octane. Is the c63 mapped for 95? I'd have thought it would be 98 only.
Generally when you factor in the increased cost of 98 the effective cost per mile is about the same. I believe that 98 has better detergents for the injectors but I could be making that up! But otherwise the advantages seem somewhat limited unless the map makes all the difference and a car doesn't run well on 95.

 

[nico2014]

When I bought my car, I was told by AMG sales team that the engine does adapt if it is getting a lower fuel 95 but to occasionally fill it up with 98 to keep engine in good condition. As far as I am concerned, I always have filled it with 98 since the very start and would avoid the 95 if possible...

 

[Moosey]

When I bought my car, I was told by AMG sales team that the engine does adapt if it is getting a lower fuel 95 but to occasionally fill it up with 98 to keep engine in good condition. As far as I am concerned, I always have filled it with 98 since the very start and would avoid the 95 if possible...

Yeah, that's been covered here extensively before!
Mine has only seen V-Power since I've owned it.
Since the engine is designed to run 98 - I'm not surprised at it being better than on 95 but the difference is stark!