premix increase in MPG?

[AndyBrad]

Ok only on my third tank with 200ml per tank on an R3

I do a lot of short trips and usually get about 150-160 to a tank. Since premixing im getting 180-200!?

any thoughts? has anyone else experienced anything like this?

[delta0]

Premix should help keep carbon down (as far as I am aware) so perhaps that is helping with mpg.

[Essex2Visuvesi]

Something else to bear in mind is the weather... its been cooler so the A/C is probably not working as hard

[AndyBrad]

true but i class that as a substantial increase.

[warpc0il]

Even 200 miles per tank isn't that good for an R3, with it's larger tank, so I suspect that there are other variables involved.

Short journeys do significantly reduce mpg, as do multiple cold starts.
Has your journey profile changed around the same time, e.g. have you done at least one longer journey per recent tankful?

Have you honed your driving technique, e.g. using more of the mid-range revs rather than labouring at low revs?

Have you done anything else to the car, either to the the engine or brakes?
Could the brakes have been sticking, e.g. car not used much previously, and now running more freely?

[AndyBrad]

nothing changed on the car.
its generally short trips using all the revs. nothing has changed.
Ive never had good mileage due to my heavy foot.

[Ian9]

I wouldn't have thought premixing would help that, keeping things clean yes but that's it. I think it's probably the same as using vpower ect ie helps clean things. I do it too but don't expect an mpg increase.

I'm probably wrong though : )

[warpc0il]

Have you pumped the tyres up?

[PeteH]

The first question is, is it real or not?
If it's a real change then the second question is, was it a consistent difference while using pre-mix, or a one-off step change due to the pre-mix "fixing" some issue?
If it's the first one then you should keep using pre-mix, because it's saving you a huge amount of money.
If it's the second one then you could stop using pre-mix until you see the "problem" return, because pre-mix is costing you money.

If you assert that it's both real, and that pre-mix inherently improves your mpg, then I'm sceptical. The only way I'll believe that is if someone did the science. The test would be something like this:
Fill your car right up, with pre-mix. Take it 150 miles up a quiet motorway, with the cruise control set to 70mph, turn around, and drive it 150 miles back with the cruise set to 70 again. Now refill the car right up again without premix, and note exactly how much fuel you put in. Then repeat the journey is accurately as you can. Brim the car again, and note how much you put in. This will take you about 10 hours, and be as boring as hell, but you'll get the answer to your question.

My money is on there being no statistical difference. I'll even put my money where my mouth is. If the pre-mix journey is more than 2mpg better than the non-pre-mix journey I will personally pay for the two tanks of fuel

[AndyBrad]

yup.
my guess is its changed something. as suggested lots of carbon from short journeys could be one.
I'll keep monitoring it.

[Essex2Visuvesi]

yup.
my guess is its changed something. as suggested lots of carbon from short journeys could be one.
I'll keep monitoring it.

The good old Italian tune up... could be the car was a little gummed up and some heavy right foot action has helped clean it out

[Ian9]

A E2V above said too like you Andy I too do a few short trips and get the eml on quite often and I'm sure it's the carbon build up causing it because after opening the taps for a few miles it clears. It reminds me of my the 2st days of power bands and premixing ie clogging up till you keep on the throttle and the sputtering clears.

[warpc0il]

@Ian9 You ready need to get that EML code read
viewtopic.php?f=25&t=43997

EML's that come and go are a symptom of a persistent problem that is triggering most but not quite every time you drive the car.

Most of these point to something that could be easily fixed and may have a huge impact on drivability, fuel economy and performance.
However, failure to rectify could cause serious (read expensive) damage.

[Ian9]

Thanks warpcOil

I guess I'm wrong thinking it's carbon, sorry

I read your link it doesn't flash but on intermittent I got po171 last week with my small reader.

[AndyBrad]

aye its possibly running lean? get it looked at

it gets taken to the beep every day tbh so im doubting its the tuneup else i would have agreed.

[warpc0il]

That code diagnoses to...

Screenshot (9).png

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which is a very similar list to...
viewtopic.php?f=6&t=78150&start=17

[PeteH]

Rised oil pressure?

Mazda, sponsored by Google Translate.

[warpc0il]

Pauline spotted that and said "You've spelt it wrong"

"No", says I, "That's a screenprint, it slipped through Mazdas spill chocker"

[AndyBrad]

Ok spotted, this. I thought i was imagining it before but it seems not.

So i get to the last 1/4 of a tank at about 120 miles and then the next day the needle moves back up to 1/2 a tank!!!! but im not running out of fuel

wtf?

[Essex2Visuvesi]

Sticky fuel sender?
Easy check is to see how much it costs to brim the tank

[AndyBrad]

yup, im still using the same amount of fuel. as im im not running out and it costs the same to fill up (i brim it every time)

[PeteH]

A random thought then: I wonder if there is anything about adding pre-mix that can cause the sender to misbehave? It's a bit hard to think what might, but if the oil covers the float, or gets onto the electrical contacts, or gums up the pivot point, or changes the density of the fuel (especially with low fuel) it's vaguely possible that it could cause weird issues. Perhaps leaving it overnight causes the oil to be properly dissolved into the fuel, and fixes the issue.

This is a stretch, I know, and I probably don't believe it myself. But it would be an interesting reason for apparently different fuel consumption.

[AndyBrad]

im honestly stumped.

tempted to not put it in the next tank to see. but also like the fact that im getting an extra 30 miles to a tank

[AndyBrad]

Ok next tank. I dropped in 400ml of premix with standard fuel.

Bit of bogging down up to 5krpm initially but his seems to have smoothed off. runs and starts just fine. but not as quick off the mark by the calibrated sop dyno

Increase in mileage to just over 100 miles to the first half of the tank (usually 75)

interesting.

So next test do i go for more or less?

[mrspiller]

400ml per tank is already excessive, waaay more than I would use, even on track.