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Hi All,

I'm about to purchase a W177 A35 but I notice it take 98 RON which I believe is the premium unleaded and rather expensive.

Q - What fuel grade does everyone else use? and does it really matter for everyday driving?
Q - Whilst I'm at it how is the UK tax?

Cheers
 

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The car will run on 95RON(Standard unleaded) but it much prefers 97/98 RON. As a test I looked at MPG for a few tankful's of normal unleaded vs the same number of tankfuls of super unleaded. The Super gave much better MPG, which more than offset the extra cost, so not only did it work out cheaper it also gave me more peace of mind.

UK Tax. Ask us again on December 13th :)
 

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Interesting real world comparison, NJS. I'm surprised it makes such a noticeable difference. I think the premium fuels tend to contain more cleaning additives as welI which is another good reason to use them. We don't do huge miles so run all our cars on 98 RON and I think the small extra cost is worth it.
 

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Interesting real world comparison, NJS. I'm surprised it makes such a noticeable difference. I think the premium fuels tend to contain more cleaning additives as welI which is another good reason to use them. We don't do huge miles so run all our cars on 98 RON and I think the small extra cost is worth it.
It worked out at about £1.56 per tank cheaper to run on super. Which in the scheme of things isn't much, but well worth the knowledge that the car is running optimally and isn't running a greater risk of knocking due to the lower octane.
 

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I fill up with Shell V-Power which is 99RON. On the occasion I've used Tesco Momentum (99RON) or BP Ultimate (97RON) when no Shell station was nearby. I've never used 95RON in my A35 yet. Having said all that I'm one of the lead footed individuals who likes to drive about in Sport+ a lot. Consequently my MPG is not great - avg 27.4 mpg over the last ~4k miles according to the Mercedes Me app. Thankfully I have a fuel card - PHEW 😝
 

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I've been running 95 RON Shell the last couple of months and have seen no noticeable difference to consumption or performance, still at 35 mpg overall after the last 1500 miles on 95 RON and 9000 miles total.

What I have noticed is 14 pence per litre less at the pump. From what I've experienced it is rather difficult to see how the fuel consumption would increase so much on 95 RON to more than eat up that 11% price difference, particularly when there is only a 4% RON difference between the two fuels to begin with.

That kind of energy drop per unit volume appears to be all but indistinguishable with normal driving, which isn't exactly demanding much from the engine.
 

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best to go by the recommend RON in manual
For sure. I've honestly never understood people who opt for expensive performance cars then use RON95 to refuel, even though the manual says RON98. It's as if the engineers who made the car don't know what they're talking about.
 

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For sure. I've honestly never understood people who opt for expensive performance cars then use RON95 to refuel, even though the manual says RON98. It's as if the engineers who made the car don't know what they're talking about.
exactly that (y)(y)(y)(y)
 

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If you want all of the 306hp (or more) available, you have to use 98RON.

If you're not bothered about all of the 306hp, stick in 95RON, the ECU will retard the ignition to cope with 95RON, but you won't be getting 306hp.

You want more power, you have to use the higher octane fuel.

(In modern turbo cars, the MON rating is more relevant than RON. The MON figure is derived from a more demanding test, more reflective of todays engines, with slightly higher RPM, higher head loads imposed during testing. )


Interesting Honest John article about Supermarket Fuel, and 95 v 98:

 

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If you want all of the 306hp (or more) available, you have to use 98RON.

If you're not bothered about all of the 306hp, stick in 95RON, the ECU will retard the ignition to cope with 95RON, but you won't be getting 306hp.

You want more power, you have to use the higher octane fuel.

(In modern turbo cars, the MON rating is more relevant than RON. The MON figure is derived from a more demanding test, more reflective of todays engines, with slightly higher RPM, higher head loads imposed during testing. )


Interesting Honest John article about Supermarket Fuel, and 95 v 98:

another sensible answer but expect nothing less from you lol
 

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For sure. I've honestly never understood people who opt for expensive performance cars then use RON95 to refuel, even though the manual says RON98. It's as if the engineers who made the car don't know what they're talking about.

Entirely agree.

I use Tescos and have tried, Shell, BP, Texaco and a couple of others. Only Shell and Tescos give 98 Ron plus and has worked for me. My new A45s due in March will get the same.
 

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Guys and Gals, I really wouldn't use Tesco 99 Ron fuel or any supermarket fuel to be honest. A couple of months ago I put in the Tesco stuff, where I normally use Shell V Power exclusively, and almost immediately after the car through up a check engine light. Following diagnosis, it was found to be a faulty O2 sensor, post cat. I know that this could be coincidental, but strange that this happened after three years of trouble free motoring, where the only fuel I used was Shell.

For me, it's not worth the risk with supermarket fuel, just to save a little money.
 

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I run my A45 on Tesco 99 exclusively (I might put Shell V-Power in every 10th tank if I’m passing), and have a tuning box, so get around 420bhp, regularly enjoy max acceleration and drive the car hard.

I would say that your sensor failure is probably co-incidental.

All fuel, supermarket or branded, is refined together and stored together at the same refineries across the country.

Tankers of all brands draw the fuel from the same storage tanks, the only difference is each driver punches in a specific code which dispenses the company’s unique additive pack.
 

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I would tend to agree with @veeeight . It's highly unlikely one fill up of Tesco's Momentum 99 (I think that's what it's called) would cause any kind of fault in your car by itself @Chow Gar. Must be a coincidence
 

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i used Tesco Momentum for the A45 the M235 and even now on the DMS mapped 320 and have had no issues what so ever
 

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I run my A45 on Tesco 99 exclusively (I might put Shell V-Power in every 10th tank if I’m passing), and have a tuning box, so get around 420bhp, regularly enjoy max acceleration and drive the car hard.

I would say that your sensor failure is probably co-incidental.

All fuel, supermarket or branded, is refined together and stored together at the same refineries across the country.

Tankers of all brands draw the fuel from the same storage tanks, the only difference is each driver punches in a specific code which dispenses the company’s unique additive pack.
hi, what tuning box are you using? Thanks
 
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