Premium or regular unleaded?

[mtb_gary]

I've been running regular unleaded in my '96 HSE without any problems. but I notice on a few posts some are using premium unleaded. Is this how the Thor motors are getting the better fuel consumption by paying more at the pump?

[redandy3575]

I've been running regular unleaded in my '96 HSE without any problems. but I notice on a few posts some are using premium unleaded. Is this how the Thor motors are getting the better fuel consumption by paying more at the pump?

I've been using the regular unleaded on mine which too is 96 HSE and runs fine on it. I did try the 95 premium a while back, though I did notice a slight improvement in smoothness and responsiveness, I did not gain any better economy out of it. So you have to ask yourself, is it really worth spending the extra 10 cents per litre for no economic gain?

Also the Australian spec P38's are low compression motors anyway, so they really don't need the higher octane.

One thing I would not suggest using is using E10. And that is despite the VACC website telling you otherwise. The P38's are too older vehicle too gamble on the E10, eventhough they say its safe too use, you need to remember that the P38 was built before the ethanol craze, and weren't built with ethanol in mind. The newer models I.e L322 or the latest series 4 built from 2005 onwards would most likely have no issues on the E10 being a later vehicle, but not the P38. In fact I'm convinced that my fuel pump failed as a result of using the E10 previously.

[Hoges]

:oops2:sorry ..double post

[Hoges]

FWIW The additional issue with E10 is that it can play up with the fuel gauge sender. The gauge can become erratic only ever reads half full...the only option appears to be replacement of the sender. There's a Tech Bulletin about it somewhere...

Apparently service stations don't have to advise you that they've diluted the 91 ULP with ethanol... Personally I always use 95. The extra $7 or so for an average 70L fill I reckon is worth it for the relatively low miles I drive. The engine does run more smoothly. What with the see-saw prices with a 15-20 cents /litre swing and supermarket dockets... life is too short and it's a damned side cheaper than stuffing around with bung senders.

EDIT: the energy output per unit of E10 blend is considerably less than straight ULP, so the increased fuel consumption and reduced power output in the Rover V8 which is not specially tuned for Exx blends more than offsets any cost savings

[redandy3575]

FWIW The additional issue with E10 is that it can play up with the fuel gauge sender. The gauge can become erratic only ever reads half full...the only option appears to be replacement of the sender. There's a Tech Bulletin about it somewhere...

Apparently service stations don't have to advise you that they've diluted the 91 ULP with ethanol... Personally I always use 95. The extra $7 or so for an average 70L fill I reckon is worth it for the relatively low miles I drive. The engine does run more smoothly. What with the see-saw prices with a 15-20 cents /litre swing and supermarket dockets... life is too short and it's a damned side cheaper than stuffing around with bung senders.

EDIT: the energy output per unit of E10 blend is considerably less than straight ULP, so the increased fuel consumption and reduced power output in the Rover V8 which is not specially tuned for Exx blends more than offsets any cost savings

you have to be carefull as 10% additionof ethanol is also the case with some 95 & 98 octane fuels. United do it and call it Boost 98 or 100.

But what you need to remember is that higher octane is a delay in detonation, therefor your engine management needs to make adjustments in timing to gain the full benefit of both power and economy. The trouble is a lot of people get conned into buying the high octane based on the selling methods used by oil companies cause there is a higher profit margin to be made. But what they don't tell you is the truth that not all cars need it, such a base model Holden Commodore or Ford Falcon as they are specifically tuned for running on regular 91 octane. It's not say that you can't put the higher octane in, but you won't gain anything out of it. The P38 does have I'm pretty sure a variable engine management system installed ( Please correct me if I'm wrong) so there is a little bit of performance gain to be had. But I have been informed that 95 premium is a finer fuel and therefor you do tend to use a little more, kind of equalling what you'd use in the regular stuff, but with the added performance.

I think if the fuel prices are cheap enough, I'd say buy it and trial is the best way to find out.

[Hoges]

Yeah...I stay clear of some of the independents for that reason. Usually go for Caltex. My now departed VX Comm LS1 was tuned for 91, and went OK. SWMBO's 2005 1.8 Astra definitely performs better with 98 Octane esp on a long trip where it holds the hills in top at 95 kmh whereas on 91 it "always" drops back to 3rd...but they tell you that in the owners manual... :angel:

[benji]

Thats quite true redandy. The higher the octane rating the higher the calorific value (more calories per ml), and the more calories that are to be burnt the longer this process takes, so timing needs to be advanced for higher octane fuels.

All modern cars have knock senors which detect pre-ignition (knock) so the ecu can adjust spark (and injector) timing but only to a preprogrammed amount.

Lpg is 110 octane (afaik) and the GEMS system cant advance the ignition to that amount, but it certainly can for 95, though it may take a while to advance the timing as GEMS is pretty slow.

Maybe the older vn/vp might not notice the higher octane but the d.i. motors certainly do.

[mtb_gary]

Interesting discussion. I've learned a lot! Thank you to all who have contributed. As I'm not having any problems with the Caltex 91 octane I think I'll be sticking with it. Thanks once again for all your inputs, it never ceases to amaze me the knowledge database that is in this forum ;)

[redandy3575]

One thing I have been warned is to be careful with the 98 premium as they tend to actually clog injectors on cars tuned for 91 regular. High performance cars have slightly larger nosilled injectors to prevent this, as 98 premium is more dense and of a thicker composition, where is the 95 premium is completely the opposite and finer, which may explain why some cars run better on 95 than 98. So there is another reason to read and double check your owner manual & manufacture specification to make sure that your car is suitable or let alone requires that fuel, and not to take the oil companies word.

[33chinacars]

Two personal observation FWIW.
Wifes previous car , a Hyundai Santa Fe 2.7 V6 always ran smoother on higher octane fuel. It also averaged an extra 50-80 kms per tank full
My P38 MY98 4.6 also performed better on the good stuff (98 octane). Smoother & better mileage.
Both used to get 95 or 98 octane every 3rd or 4th tank full. You could feel the difference. Have been told that there are extra cleaning agents in the 98 octane fuel. So no need to add injector cleaner to your tank.

Gary

[DandT]

I personally avoid ethanol additive fuel, as I've problems with it in the past. In the Range I'll usually use 95 or 98 but have used 'non' ethanol 91 before (not e10 but I think they only have to advertise it as ethanol when its above a certain percentage?) I have to say for the extra couple of dollars per tank, the 95/98 gets my vote. I dont about economy tho, as I tend to floor it often when I'm running the higher octane :burnrubber: so my economy is ruined anyway! :p

[PaulP38a]

I also avoid E10 and usually run 95, with the odd 98 to give a bit of a clean. Didn't notice much difference between 95 and 98 on either the 4.0 or 4.6 motors.

[Mick_Marsh]

The Mercs, I run 98.
The Commodore, I run 95.
All other vehicles I run 91 with the occasional tank full of 98 to clean the fuel system.
The cars do run better on 95.

Also beware of bad fuel. I always try to fill at a BP. I have never had any bad fuel there.

[Keithy P38]

I agree with Mick - I have only ever filled up at my local BP except when I'm on a remote trip and have no other option. Even then I still look out for a BP if I can...

Mine lives on 95 premium. Nothing else.

My last tank I averaged 12.14L/100km with mixed highway/low range/town driving...

Works out that I get around 700km before the fuel light comes on...

Cheers
Keithy

[PaulP38a]

Interesting Keithy, I usually fill up at Caltex and use Shell where I can. Tend to avoid BP for philosophical reasons, but your figures make for a compelling reason to reconsider.

[superquag]

Back in my mis-spent youth.... I bought a brand new HZ Holden V8, the 4.2litre/253.
Apart from being a tad thirsty for its "power"...,it ran smoooothest on CALTEX, - which gave the worst mpg's, but gave a mpg or so more on BP and I think SHELL.
(it was a very long time ago....)

My daily driving was consistant enough to do the "A" / "B" comparisons with good repeatability. Only .08 to 1.2 mpg differance, but it was predictable.
- Average was 17 mpg.... :o

At the moment, I'm running UNITED E10 in their 95 octane. I've also advanced the timing a bit.... not far enough to hear any pinging on 'normal' 91.
So far, it seems to be running happier and I suspect better economy, but we'll have to wait for my new (non-leaking) fuel tank from LRA so I can obtain accurate figures.

Hope that helps. :)

1995 Classic Vogue SE, 3.9 gutless wonder...

[benji]

There are a few 95 and 98 fuels out there that are a 91 with an octane booster, not a true cracked 95/8. The comments here are pretty much on the ball.
Some fuels have a few % ethonol mix and sold as standard fuel too - and thats not limited to the small chains or independents.
I normally use bp 95 where I can, and the cheapest lpg I can find.

[Mick_Marsh]

Interesting Keithy, I usually fill up at Caltex and use Shell where I can. Tend to avoid BP for philosophical reasons, but your figures make for a compelling reason to reconsider.
There is nothing wrong with Shell or Caltex. Years ago I did regularly get bad fuel form Shell servo's for a while. At the time, filling up with Mobil solved the problem so I stuck with them. When they disappeared, I tried BP. I haven't had a problem with them so I have just stuck with them.