A P38s' preferable octane

[Sidewinder76]

Hi all.

Which octane is best for a '98 4.0? 91, 95 or 98?

Thanks.

[p38arover]

What CR number is on the block near the dipstick? If it has CR 8.36:1, it's low compression and 91 RON is fine.

https://www.aulro.com/afvb/images/imported/2012/04/570.jpg

[bee utey]

Hi all.

Which octane is best for a '98 4.0? 91, 95 or 98?

Thanks.

Check your compression ratio, its next to the engine number, next to the dipstick tube. If it's a standard 8.13 compression just use 91 octane but steer clear of ethanol containing fuels if you can.

Edit: As Ron said:D

[p38arover]

f it's a standard 8.13 compression

I thought it was 8.13:1, too. In fact, I'd typed that then decided to check my engine(s). Here's a closeup of another engine and like the one above, it definitely reads 8.36:1

Odd.

https://www.aulro.com/afvb/images/imported/2012/04/569.jpg

[Hoges]

In the Owner's Handbook LR recommends 91 as a "MINIMUM" RON for the low comp engine . I generally run 95 (and give up drinking red for a week to make up the difference in $$:eek:) There's less tendency for it to ping with the higher RON fuel, esp. on hot days.

[Keithy P38]

I always run 95 in mine, had no choice but to use 91 at the Palmer river roadhouse, got better highway economy on it than I do on premium, however I did notice a much smellier exhaust. Mine's a 99 Bosch 4.6 (unsure of my compression ratio).

Cheers
Keithy

[33chinacars]

Always ran 95 in my 4.6 MY98. Went much better than on 91

Gary

[Marshall]

(and give up drinking red for a week to make up the difference in $$:eek:) .

I saw an episode last year on a motoring show where they did a live test using the three types of fuel. As it turned out, the cars economy improved with the more expensive types so much so that the price difference was negligible. I would be interested in personal experiences...

[PhilipA]

I saw an episode last year on a motoring show where they did a live test using the three types of fuel. As it turned out, the cars economy improved with the more expensive types so much so that the price difference was negligible. I would be interested in personal experiences...

Horses for courses
A low comp no knock sensor engine will get no benefit from higher octane.

A high compression engine with knock sensors tuned for say 95 or 98 octane (eg BMW , VW ) will get significant benefit from the octane it was designed to use as the timing will be retarded using lower octane .

A clean Gems 8.36:1 or even Thor motronic 8.36 .1 should gain no benefit, although a carboned up Motronic may due to more advance being tolerated without Knock.
Regards Philip A

[Hoges]

I have done several trips from BNE < - > CBR in the (Thor) P38 over the past couple of years ...pretty much same load, same schedule, same route... once on 91 and once on 98 the whole way and back. The difference (using GPS distance and pump values) was 1.3 L/100 km in favour of the 98 octane (14.1 vs 12.8). For the others I used 95. ...about 13.2 L/100km.

[benji]

I was of the impression that all p38s were LR approved to run E10? I personally wouldn't touch the stuff, but if I was travelling and it was all they had it's nice to know it'll run on the stuff.

Also, many 'performance' chips require 95 or greater, this just means that when I do the cape, fraser, or simo etc. i've got to carry an octane booster.

In RAVE it states that low compression is 8.23, but on my block (i've just checked it) it also states 8.36.

[PhilipA]

So the difference in economy at 10.1% is less than the % difference in price as long as you are not in the boondocks where you cannot get 98 anyway.
Motormouth today prices in Northern Beaches of Sydney ULP 147.9, PULP 98 161.9, E10 145.9
Those prices are at the top of the cycle . Drop 10c off at say 137.9 and 151.9 and the difference is just about exactly 10%. Get your coles/woolies discount and the percentage will be more.

BTW , IMHO one trip is a little short a distance to compare, and I doubt that the real difference is 10% in economy in an 8.36:1 car unless of course it has a lot of carbon in it.
Regards Philip A

[33chinacars]

We had a Hyundai Santa Fe. It always ran better on 95/98 octane fuel. Went an extra 50-70 kms per tank. May not have balanced out the extra cost but in my mind well worth the cost. On 91 engine was rough on hard acceleration ( possible pinging ) , not there on the 95. There are also extra additives in the higher octane fuels to clean injectors etc. Even if not convinced of the benifits of 95/98 fuel all the time. Its a good idea to run a tank full every 4 or 5 fills

Gary

[Hoges]

I was of the impression that all p38s were LR approved to run E10? I personally wouldn't touch the stuff, but if I was travelling and it was all they had it's nice to know it'll run on the stuff.

Also, many 'performance' chips require 95 or greater, this just means that when I do the cape, fraser, or simo etc. i've got to carry an octane booster.

In RAVE it states that low compression is 8.23, but on my block (i've just checked it) it also states 8.36.

on the contrary, LR specifically states not to use ethanol blends- there was a TSB about it. Ethanol can cause problems with the fuel gauge sender resulting in a deterioration of the variable resistor. A deposit builds up on the sender causing the gauge to indicate the tank is only half full even when the tank is topped up to the limit.... I have had experience of this having inadvertently filled up twice with bodgy fuel .... took ages and several doses of efi cleaner to get rid of the problem:mad:

[Hoges]

So the difference in economy at 10.1% is less than the % difference in price as long as you are not in the boondocks where you cannot get 98 anyway.
Motormouth today prices in Northern Beaches of Sydney ULP 147.9, PULP 98 161.9, E10 145.9
Those prices are at the top of the cycle . Drop 10c off at say 137.9 and 151.9 and the difference is just about exactly 10%. Get your coles/woolies discount and the percentage will be more.

BTW , IMHO one trip is a little short a distance to compare, and I doubt that the real difference is 10% in economy in an 8.36:1 car unless of course it has a lot of carbon in it.
Regards Philip A

Actually I considered a return trip of 3,100 km with a mix of city and highway driving each for each "event" was quite a reasonable sample for comparison purposes!;)

[redandy3575]

on the contrary, LR specifically states not to use ethanol blends- there was a TSB about it. Ethanol can cause problems with the fuel gauge sender resulting in a deterioration of the variable resistor. A deposit builds up on the sender causing the gauge to indicate the tank is only half full even when the tank is topped up to the limit.... I have had experience of this having inadvertently filled up twice with bodgy fuel .... took ages and several doses of efi cleaner to get rid of the problem:mad:

I've got a similar problem with my fuel gauge also where it doesn't show the maximum full, more like 3/4 full, but is slowly getting better after adding a regular dose of efi cleaner. According to the VACC wedsite all petrol LR products can run on E10, however as a rule of thumb in my opinion any vehicle regardless of brand built before the year 2000 should not use E10 as cars were never built with the intention of ever running on it, mainly cause it didn't exist (in Australia anyway!!). I ran mine on 95 octane for a while with the added benefit of slightly extra power, smoother & more responsive running, but didn't really get that much extra KM's out of it so returned back to standard 91 octane. I think the low comp motor will run comfortably on both 91 & 95 octane, 98 octane is just a waste of money as there was virtually no difference at all between that and the 95 octane.

[Hoges]

...They need to be very selective about which petrol engines are suitable...

Re. low compression engines etc ...my nephew has done a beautiful job of restoring a 1928 Chev (CR less than 5:1 !). He rebuilt the engine without needing to change the valve seats etc to cope with unleaded or add a lead replacement because he discovered that it runs perfectly well on Shell 98 octane will no ill effects... tells me that his old car club mates discovered this some years ago when Shell first brought out its Optimax brand

[redandy3575]

...They need to be very selective about which petrol engines are suitable...

Re. low compression engines etc ...my nephew has done a beautiful job of restoring a 1928 Chev (CR less than 5:1 !). He rebuilt the engine without needing to change the valve seats etc to cope with unleaded or add a lead replacement because he discovered that it runs perfectly well on Shell 98 octane will no ill effects... tells me that his old car club mates discovered this some years ago when Shell first brought out its Optimax brand

Yes, but you do realise that the lead in the old Super petrol is a form of lubrication, though the engine may run OK on the 98 octane the net effect of not having any form of lubricity on the valve stem will create long term problems in premature valve wear. My mate found out the Hard way when his Camaro with the 327 V8 didn't last more than 58,000 km due to not putting lead replacement additive or some form of a upper cylinder lubrication system. He had the hardened valve seats, but still wore through it quicker than normal. Also important with a newly rebuilt classic motor is to use the best quality oil within a reasonable price preferably synthetic, and these engines will last forever.

[Sidewinder76]

I have discovered that mine is an 8.23 low compression so having read the other posts (thanks all for your replies) it would seem that 91 or 95 will suffice and there is little point in running on 98? Are there no benifits at all from running on 98? Lubrication or perhaps performance?

[Sidewinder76]

I guess the other question about 98 octane is would it do any damage?

[PhilipA]

Only to your wallet.LOL
Regards Philip A

[RR P38]

There is no way known that a higher quality fuel ie 98 octane can do an engine harm.
It does take your engine management system a little time to get the most out of it as it adjusts to the better fuel.
As for using ethanol fuel i can categorically state that in 12 years of using PLUS ULP i have not had a single issue with ethanol based fuel.

[33chinacars]

I'd stay with 95 octane. Didn't use 91 if there was another choice

Gary

[redandy3575]

There is no way known that a higher quality fuel ie 98 octane can do an engine harm.
It does take your engine management system a little time to get the most out of it as it adjusts to the better fuel.
As for using ethanol fuel i can categorically state that in 12 years of using PLUS ULP i have not had a single issue with ethanol based fuel.

I run e10 when i first got the P38 and after around 12 months killed the fuel pump as a result. According to the VACC website, it states that all petrol Land Rover vehicles post 1986 are suitable to run on both e5 & e10, but as a rule of thumb, any vehicle built before the year 2000 i personally would not recommend using the e10. Vehicles before 2000 were not manufactured with e10 in mind, and even though it may be ok from a VACC's point of view, the long term effects have still not been tested, and will most likely raise it's ugly head when you least expect. Even vehicles built between 2000 - 2005 you'd want to double check just to be sure as when i last looked on VACC, i noticed some Hyundai models to be unsuitable right up until 2007, so it pays to check. As far as octane, 91 seems to be the flavour for the my 96 4.6. I did notice a slight decrease in economy (would you believe it!!) when running on 95, but noticed the cleaner, less smellier running, not to mention a smoother acceleration. 98 octane is merely a waste of money as that fuel is really made for high performance engines think Ferrari, HSV,FPV, Porsche type cars. Would probably make the P38 run worse with such a strong fuel.

[Tikka7mm08]

Just buying a 97 4.6 and on picking up need to full it up. Not sure what compression she is...choices are 91 or 95 Octane. Sounds 'safer' to just got with 95? Can get 98 but only at BP.

[wayneg]

I have had both low and High comp engined cars, always run std ulp 91 with no issues. The high comp car is LPG so dont use much petrol but when I do it runs sweet. Your car will most likely be low comp

[Tikka7mm08]

Ah righto...don't mind paying for premium but if it doesn't make ANY difference...

[mtb_gary]

I agree with Wayne, 91 octane on a GEMS motor. It's most likely a low comp motor. I only ever use 91 in mine.

Gary

[TheTree]

My MY99 bosch owners manual specifies 95 RON so I use that.

There are quite a few sad stories about E10 and P38 fuel pumps sadly :angry:

Steve

[redandy3575]

My MY99 bosch owners manual specifies 95 RON so I use that.

There are quite a few sad stories about E10 and P38 fuel pumps sadly :angry:

Steve

Yes. Mine was one of them:o