Author Topic: Would the Mk3 benefit from premium petrol?  (Read 6898 times)

peteo48

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Would the Mk3 benefit from premium petrol?
« on: February 23, 2018, 05:20:49 PM »
The recommendation in the manual for the Mk3 is the same as for the other Jazzes - 95 Octane or higher but the compression ration has seen a sharp increase with the Mk3 - it's now 13.5:1 so really a pretty high CR.

I'm thinking that this engine, more than the earlier cars, might benefit from premium fuel. Any views?


Downsizer

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Re: Would the Mk3 benefit from premium petrol?
« Reply #1 on: February 23, 2018, 06:11:02 PM »
There's been extensive (but inconclusive) discussion previously in this forum.  Personally, I'm happy with 20,000 miles on ASDA 95, giving actual measured consumption of over 50 mpg.

JazzandJag

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Re: Would the Mk3 benefit from premium petrol?
« Reply #2 on: February 23, 2018, 06:12:08 PM »
I used Tesco Momentum 99 in both my 1.3 Mk3s. I felt there was a small but nethertheless noticable increase in performance. One one occasion the car felt worse than usual and I am convinced that the 95 and 99 grades had been mixed up. On the next fill at a different Tesco all was restored to normal. I don’t think I will be needing it in my 1.5 Sport though!

Give it a go for a couple of tankfuls and then a tankful of 95 and see if you notice any difference.

culzean

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Re: Would the Mk3 benefit from premium petrol?
« Reply #3 on: February 23, 2018, 06:41:52 PM »
The recommendation in the manual for the Mk3 is the same as for the other Jazzes - 95 Octane or higher but the compression ration has seen a sharp increase with the Mk3 - it's now 13.5:1 so really a pretty high CR.

I'm thinking that this engine, more than the earlier cars, might benefit from premium fuel. Any views?

Cars with CR as high as 13.5 are normally direct injection and avoid pinking by only injecting the fuel once the air in the cylinder is compressed, that way the fuel / air mixture cannot explode while it is being compressed.  I don't know if new Jazz has direct injection but the only way to see if it is happier on 97 or 99 is to try it.   Wait till tank is pretty low before changing fuel and give it a few miles to sort itself out,  but try it on the steepest hills you can find to check for extra power and pinking (or lack of it). 

I have seen a noticeable difference in 95 and 97 in both Jazz and Civic (both with 11:1 CR ) but its really up to you,  I found that if you used the extra 'pep' you did not get more MPG, but you can notice that you need less throttle opening to achieve same speed on higher octane,  may be more noticeable on CVT actauly than on a manual - check the revs needed for a certain speed under certain conditions (like up a certain hill or 70 on the motorway on comparable sections).
« Last Edit: February 23, 2018, 06:43:48 PM by culzean »
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guest4871

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Re: Would the Mk3 benefit from premium petrol?
« Reply #4 on: February 23, 2018, 09:45:25 PM »
In my view - definitely  Yes.

I use Shell V Power exclusively.

Not for any reason of performance or octane rating (which I think is probably a little "old hat" these days as explained above) but because of the quality of the additives.

I do a relatively low mileage so any difference in cost is relatively small and the additives work much better the older the car is.


mikebore

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Re: Would the Mk3 benefit from premium petrol?
« Reply #5 on: February 23, 2018, 09:46:20 PM »
I switch between 95 and Super (97?....not seen 99 on a pump). I have not seen difference in fuel consumption (I keep pump to pump records) and for performance don't think I could pass a "blindfold" test...ie say which fuel was being used without knowing.

For years I believed that if it didn't pink there was no benefit in higher octane, BUT, as I understand it most modern engines automatically adjust the timing to just avoid pinking. If this is the case there is a technical reason why performance/economy might be better with higher octane, but I have not been able to detect it.

123Drive!

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Re: Would the Mk3 benefit from premium petrol?
« Reply #6 on: February 23, 2018, 09:49:32 PM »
I have a MK2 i-Shift and have only driven on normal petrol until summer of 2016, I was driving on a long journey and so have a go at Shell V-Power. Wow! The car is so much powerful and holds at a certain gear before changing to a higher gear thereby giving more power. Also a small notice of about  2 miles extra per tank. If you join the Shell Club, you get a voucher every 4 months and it pays back the extra costs. I have never gone back to standard petrol unless I can't find a Shell nearby. I have also used Tesco premium petrol and find it good as well and the extra few pence, definitely worth it. My pupils, I am driving instructor, noticed when I filled with standard petrol. So it's not just me being sensitive!

Try it and see how it goes! Have fun.

Jocko

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Re: Would the Mk3 benefit from premium petrol?
« Reply #7 on: February 23, 2018, 10:31:47 PM »
I tried Shell V Power in my Mk 1 and felt the car ran a bit smoother. There was a slight improvement in fuel economy but felt the 68p a gallon extra, I was having to pay, did not make it a viable option.

peteo48

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Re: Would the Mk3 benefit from premium petrol?
« Reply #8 on: February 23, 2018, 10:47:12 PM »
Just on price - re Jocko's post - I notice that the price premium on Tesco and Sainsbury's "super" fuels is 5 pence a litre but the brand names all charge 10 pence a litre extra. I wonder why that is. Tesco claim that their Momentum fuel has additional additives over the 95 Octane.

culzean

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Re: Would the Mk3 benefit from premium petrol?
« Reply #9 on: February 24, 2018, 07:38:07 AM »
I switch between 95 and Super (97?....not seen 99 on a pump).

Tesco do 99 and I tried it once (we were passing the Tesco garage) when going to Wales with full load of passengers and luggage in the Civic, it just flew up those welsh mountains and even the steep and bendy road up to Harlech castle no bother,  went up in a higher gear than I thought it would.   There is actually less power 'contained' in higher octane because the additives to raise the octane either don't burn or are less powerful (ethanol) but by being able to advance the spark the engine can make much better use of the fuel.  I tried high octane in one of my older motorbikes and it actually ran worse because with timing set for lower octane and no ECU / knock sensors it could not move the spark around.   The closer the spark fires (retarded to stop knocking) to top dead centre of stroke the less time the charge has to burn properly and the more of its force is wasted.  If spark fires too early (advanced) with lower octane the expansion of the igniting charge raises cylinder pressure and causes the lower octane around the edges to explode before it should,  it then tries to push piston down the same way it just came up without passing TDC,  the forces are large and that is why pinking / knocking can wreck your engine in very short order - by trying to reverse crankshaft every time a cylinder fires.
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mikebore

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Re: Would the Mk3 benefit from premium petrol?
« Reply #10 on: February 24, 2018, 08:02:20 AM »
I can't help feeling that if the benefit of 97/99 octane fuel was really as great as some people claim, then Honda would say something like "Recommended octane 97/99. Minimum octane 95", rather than let the vast majority of their customers drive around with a sub-optimal performance.

peteo48

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Re: Would the Mk3 benefit from premium petrol?
« Reply #11 on: February 24, 2018, 08:26:12 AM »
I can't help feeling that if the benefit of 97/99 octane fuel was really as great as some people claim, then Honda would say something like "Recommended octane 97/99. Minimum octane 95", rather than let the vast majority of their customers drive around with a sub-optimal performance.

That's a very good point and some expensive cars often say premium recommended. The wording in Honda manuals (and also in Toyota) is "95 Octane or higher"

You can see why lawyers deal in semantics! What are they saying here? What does "or higher" mean? Anybody knows that you can put premium fuels in any car so why say "or higher?"

I don't think for one moment that 95 Octane from any supplier (like supermarkets) will do any harm but I wonder if there are benefits to be had. I bunged some Tesco Momentum in the car yesterday but it will be mixed in with whatever was left in by the dealer. Might go with, say, 3 tankfuls then go down to 95 and see if I notice anything.

mikebore

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Re: Would the Mk3 benefit from premium petrol?
« Reply #12 on: February 24, 2018, 08:29:07 AM »
Someone mentioned earlier the additives in the higher octane fuels. I can believe the cleaning effect more than I can the performance effect, and there might be some benefit in using higher octane every few tankfuls for this reason.

Jocko

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Re: Would the Mk3 benefit from premium petrol?
« Reply #13 on: February 24, 2018, 08:47:23 AM »
I added a bottle of Redex Petrol System Cleaner to a couple of tankfuls. Didn't notice any improvement, but I will probably do the same again this year. Found Asda the cheapest place to buy it.

Downsizer

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Re: Would the Mk3 benefit from premium petrol?
« Reply #14 on: February 24, 2018, 09:24:49 AM »
As I mentioned elsewhere, my dealer added Wurth petrol additive at the first service, but not at the second.  As I didn't have anything to pay, I didn't ask the reason.  It seems to be associated mainly with motorbike engines, so perhaps they got a bit confused!
« Last Edit: February 24, 2018, 09:31:45 AM by Downsizer »

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