I moved house recently and Tesco is really the only convenient place for me to get petrol now, but it has SU so I wasn't too bothered.

Coincidentally I had been getting crap mpg lately. Being on a new commuting road I didn't think much of it until the other day. We were back up visiting the folks and I filled up with VPower.

Next day after a long run I quite suddenly notice how smoothly the engine was running. Checking the comp my mpg was about 4mpg higher than I was expecting. Back on the commute it is staying about 4mpg higher than I has been getting on Tesco SU.

That's as big a difference as I would expect between normal 95RON and 99RON but between two SU brands. How crap is Tesco making their fuel these days!

Has anyone done a comparison of Shell 95RON Vs Tesco 99RON?

i used to use shell V-power but changed awhile ago to tesco 99 and find no difference between the two. it must be good fuel because its used in the seat cupra cup races.

I tried tesco petrol once, and the car ran like a sack of poo. Never again, it's cheaper for a reason.

Thats my experience of it too , car runs ok but the difference over a couple of weeks is definately noticeable, strangely enough was intending to post this virtually word for word.

I've always run the car on a mix of Tesco and Shell super unleadeds.

I'd never noticed a difference until now.

I wondered if Tesco is cost cutting on their fuel.

Edited 23 December, 200916 yr by Aspman

Never found a difference between the two 99rons

Never found a difference between the two 99rons

I'm a fan of the 2 ronnies , clever humour , four candles ... lol.

I'm a fan of the 2 ronnies , clever humour , four candles ... lol.

Love it!

Well it's goodnight from him etc lol

Shell is extremely over priced at the one station they have in Cardiff so I don't bother.

Well it's goodnight from him etc lol

Shell is extremely over priced at the one station they have in Cardiff so I don't bother.

I have started using vpower 99 the last few tanks of fuel, but before i used tesco 99. not noticed a difference in performance,or mpg

i have changed purely as there is no difference in price between the two. and since tesco 99 has additives to make it 99 octane, whereas the vpower is refined to be 99 octane

Wonder if its a map thing , deffo can see the difference on the average mileage reading , not huge but noticeable

Wonder if its a map thing , deffo can see the difference on the average mileage reading , not huge but noticeable

my mpg is down recently i have put it down to the cold weather though

this is depressing , winter costs u more as well

1. More idling

This should be a no-brainer, yet parked idling cars are a common sight in cold weather. Resist the temptation to idle your car to warm it up. An idling engine gets 0 mpg. Consider also that idling the engine does nothing to warm up the tires and drivetrain.

Even in the coldest weather, you can begin driving after 30 seconds from a cold start - keep speeds low/moderate and use gentle acceleration until the temperature gauge starts to climb (source).

2. Low tire pressure

Of course you're smart enough to keep up your tire pressure as the temperature drops, right? A 10-degree (F) change in ambient temperature equates to a 1 psi change in tire pressure (source). Fuel economy declines 0.4 percent for every 1 psi drop (source).

3. Increased rolling resistance

Even if you're completely attentive to proper tire pressure, cold ambient temperatures will still cause your tires to return worse mileage. That's because a tire's shape isn't completely round - the sidewall bulges out at the bottom, and where the tread meets the road the small contact patch is actually flat. As the tire rotates, it constantly deforms to this shape, and this deformation requires more energy when the rubber is cold and hard. Rolling resistance at 0 degrees F is 20% greater than at 80 degrees (source 1, source 2).

4. Crappy road conditions

It's increased rolling resistance of another kind: driving through slush and snow. And then there's its wasteful polar (no pun intended) opposite: no friction at all! (A.K.A. wheelspin on ice.)

5. Lower average engine temperature

In the winter, an engine takes longer to reach operating temperature and cools off faster when shut off. Since the engine management system orders up a richer mixture when cold (proportionately more fuel in the air/fuel combination), more fuel is being burned overall.

A block heater can offset this problem (improving fuel economy by 10% in sub-zero conditions - source), as can garage parking, and combining trips (to minimize the number of cold/hot cycles).

Also related...

6. Higher average lubricant viscosity

Engine oil thickens as it cools. So does transmission and differential fluids and even bearing grease. Significantly more energy is needed to overcome the added drag these cold lubricants cause.

Using synthetic fluids can address this problem, since their viscosity changes less at extreme temperatures than traditional mineral fluids.

7. Weaker gasoline

Gasoline doesn't vaporize readily at very cold temperatures. So oil companies formulate fuel differently for cold-weather markets in the winter. Unfortunately, the changes that provide better cold vaporization characteristics also result in less available energy for combustion. You won't get as far on a liter of winter gas as you will on a liter of summer gas. (Source.)

8. Higher electrical loads

In colder temps, you use electrical accessories more often:

- lights (in higher lattitudes it's darker in the winter)

- rear window defroster (because it's easier than using the ice scraper, right?)

- heater blower motor (I don't have a/c, so this isn't balanced out during warm conditions); heated seats/mirrors

- windshield washer pump (because it's easier than using the ice scraper, right? And for frequently cleaning off dirty road spray.)

9. More aerodynamic drag

No, I'm not referring to the layer of snow you're too lazy to brush off the top of the car (though that would hurt mpg too).

A vehicle�s aerodynamic drag is proportional to air density, and the density increases as temperature drops. For every 10 degree F drop in temperature, aerodynamic drag increases by 2% (source).

I averaged 5.3 MPG on the way to work today

Average MPH was 2... took nearly an hour and a half to crawl just over 3 miles!

Wonder if its a map thing , deffo can see the difference on the average mileage reading , not huge but noticeable

My VRS is totally standard.

I can't see I'd seen a difference between the two until now.

It's like Tesco was filling the SU tanks with UL and then selling it at a higher price (allegedly).

very true pete.

my car since this wetaher went downhill has dropped a massive amount. my car does not like crawling around and hates traffic lights even more. i reckon my average ahas dropped from about 24-26mpg around town to less than 15mpg.

I averaged 5.3 MPG on the way to work today

Average MPH was 2... took nearly an hour and a half to crawl just over 3 miles!

Yeah but crawling home from the pub first doesnt count andy

I prefer vpower when I can get it, but is it worth in this weather?

VPower is always worth it.

Especially since your engine has been mapped for the higher octane fuel.

I use both (v-power and Tesco99), can't say that I notice a huge difference either way.

Then again my car seems less picky since it has been remapped...

Ethanol contains less energy than petrol per unit volume. It is an octane modifier. it can be mixed with petrol up to about 15%. Theoretically a car using ethanol would be less economical just in the same way as petrol is less economical than diesel. Octane is a measure of a fuels resistance to knocking or self combustion. Unless an engine needs high octane fuel their is nothing to be gained in using it. usually engines with high compression engines need high octane fuels to reduce the effects of preignition and power loss. An engine not designed to use high octane fuel could in fact do less miles per gallon and produce less power. Only use the octane grades recommended for your car for the best results. Tesco have large shares in bioethical production, it is in their interests to promote and sell it. Their are some green arguments for using bio fuels.

I've only filled up with Tesco 99 once... and I'll never do it again!

Back when I had my 911, I filled up at the local Tesco... my thinking being - they use it in the British Rally Championship - so it can't be that bad....

Coincidence or not, the car wouldn't rev cleanly passed 3k... I thought it'd be fine, I'll just keep diluting the Tesco stuff with Vpower until it clears....

didn't work - had to shell out £700 to have parts of the fuel system replaced....

It may have been coincidence, but I'm not prepared to take the risk with any more of my petrol cars!

Shell all the way!

Isolated incident!

Isolated incident!

that maybe so....

but I'm never taking the risk again

Tesco 99 for me all the time my vRS loves it. Have posted this link before but here it is again...

http://www.thorneymotorsport.co.uk/tuning/Fuel_Test_Results_Update.shtml