MPG Factors

Tesla

Tesla

Tesla

Soldato
Joined
19 Jan 2003
Posts
17,577
Location
Bristol, UK
Hi there,

When I bought my van off of it's original owner the trip was showing an average of 50MPG over a thousand miles.

Since owning the van I have never been able to achieve this. The thing that hits me is that I can only ever get the trip to peak at 50-55MPG when on a flat road doing around 50mph in 5th (top gear).

I must be doing something fundamentally wrong I guess? Over the last 1100-1200 miles I have averaged 42Mpg according to the trip.

I don't drive the van hard, I am good at reading the road, anticipating events and such. The Van never carries much weight. The previous owner carried instruments so I guess his was the same sort of load as mine. I have however fitted a full roof rack which the owner didn't have.

Perhaps it's the motorway work that cripples the MPG? I struggle to get over 40MPG from a motorway run! The trusty old Mondeo was better than that :(

Poor little 1.3 Diesel MultiJet.
Van is a Fiat Doblo Mk1.

Could it be the Tesco diesel?

The van is well maintained. Oil regulalry checked and very rarely have I ever topped it up. Only needed to once or twice over 12k miles I think. The van has been filled with Mobil1 on every service by myself and the previous owner.

Mileage is now around 32k, it had around 20k when I bought it almost a year ago.

Cheers!
 
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Did the previous owner have a flat cap and a pipe? :p

I would imagine if you have a roof rack and use it regularly then its nuking the economy a bit.

Apart from that unless you have a boost leak or a fault somewhere I cant see any reason for the drop in economy, I would put it down solely to the roof rack.

Once serviced my van (not a doblo) shows a slight increase in MPG, around 2-3 on average, the service interval is every 15k. Mine is geared pretty poorly for the motorway as it has a lack of power, hence if i knock it back from 75ish to 60 I get a fairly large fuel saving.
 
Roof rack, loading weight, air con etc etc

Different cars have different optimum driving styles - in my car I get the best economy by going 3/4 throttle in boost, backing off again, lather rinse and repeat.
 
It unfortunately lacks A/C. I'm not sure the 1.3 would have enough power to turn the wheels with the A/C engaged anyway though.

The previous owner was regular build like myself.

Tyre pressures are 2.6bar front and 3.0bar rear. I check them around once per month.

The roof rack is a full rack and I installed it a couple weeks after buying the van. It stays permanantly installed as is bolted to the proper mounting holes in the roof. Quite a pain if I was to remove it all of the time and I expect the threads would start to wear as it's not really designed for that. The front of the rack has a spoiler/lip similar to a truck cab but it doesn't seem large enough. Do you think getting a lip fabricated that lipped over the roof would benefit?

I will grab a pic of the rack to further explain later in the day.

Will try motorway runs at 60mph and see what results I get over the next month too.
 
If you're often running on the motorway at 70 and the previous owner mostly ran on A roads at 50, that would explain a lot. The roof rack could easily explain the majority of that difference.
 
Plus MPG will decrease over time anyway as parts go through wear and tear and of course if you've changed tyres, used diff oil etc - many things can change MPG.
 
Could be the diesel fuel. My car didn't do well with Shell fuel and after switching to other brand like Texaco and BP, my mpg figure has improved. My car used to feel sluggish with Shell diesel, never use it again.

I don't use supermarket fuel anymore as well.
 
I've had 3 different vauxhall combos now, all with the same 1.3 engine as you, first had a roof rack, second didn't, third didn't but has a 70mph limiter.

I get significantly more miles to a tank in the limited one than I ever did in the first 2. I never actually noticed any difference between the first and second vans with fuel economy, always got pretty much bang on 380 miles to a tank +/- 20miles, this new one with the limiter I'm approaching nearly 450 miles a tank and can only put it down to the limiter i.e. by being forced to stick at 70 (3000rpm) seems to help fuel economy greatly instead of thrashing the knackers off it to get to 80mph or so.

This new one has air con too, it redefines the rulebook on slow when you've got it on and trying to get upto motorway speeds lol
 
Roof rack = MPGKILLERZ plain and simple.

Even load in the rear and its position will affect mpg. Any load if possible should be as close to the front of the van. If you have anything heavy at the back it will cause the vans nose to rise a degree or two. Even this can cause anything up to 15-20% loss in mpg. :eek:
 
loaded roof rack has a massive impact on MPG, the other thing is harsh acceleration. Opening the throttle just enough to accelerate will give better economy, and also early anticipation allowing you to come off the throttle early rather than brake late will help (most engines now shut the fuel off on overun).
 
spaz, what sort of figures are you seeing in the combo?

I get pretty much bang on 500miles per tank everytime. The tank is around 45-50l at a guess as around £50 seems to fill it.

Roof rack is rarely loaded. If I have anything on it's just double section 12-rung ladder.
 
No trip computer in mine, but working it out, it was averaging around 42/43mpg in my older vans and about 47/48mpg in the newer one. The tank is smaller than your one, must be around 40-45L as it takes around £40 or so to fill it up.
 
As above, the roof rack is a bit of a killer.

Also try changing fuel to another brand and see if that helps.

Is there any black smoke, hesitation under throttle or anything like that?
 
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