I’m with Alex. I use 91, which is the highest readily available octane here. I live in southwestern British Columbia and frequently drive our mountain highways. It runs better on 91 than 87 and is usually around 10-12c/litre more.

 

Also, around here, 91 is usually pure gasoline without ethanol added, so that might be partly why it runs better on 91.

 

All fuel in my area SETX, contains at least 10% Ethanol. There are like a few needle in a haystack gas stations that advertise 0% Ethanol in their fuel, but they aren't local to me so I've never used them.

 

I have one station in my area with 91 pure gas but at about a $1 more per gallon than 87 ethanol I don't indulge much. I can get 91 ethanol at the Sam's club for .50 per gallon more - most driving conditions I don't notice any difference - cross country drives with hours of highway speed higher octane does seem to get better gas mileage.

 

Most stations only have high and low test and mix them for multiple grades, both grades will have the same ethanol content. High octane is only needed for High compression or forced induction. When you run 87 in one of those applications the motor will retard the timing until it is out of its prime operating conditions. It may also pollute more due to a late ignition sequence end. Ethanol is really just a filler that as a side effect increases octane. It's like the "pink slime" in ground beef. Technically it's still meat but kinda just filler. The more alcohol in fuel, the better it is for forced induction or high compression. 20% alcohol seems to be the max you can put in a non flex fuel car. Alcohol has much less fuel per gallon than gasoline. Therefore you will get more MPG from straight gas than from 80/20.

As for every land rover ever made on the face of the planet, besides the forced induction ones, you can run 87. Until very recently most Asian countries ran 80 octane. Until 2000ish you couldn't even get better than 80 octane fuel. You would just fill your 1995 discovery with 80 octane. The low compression kept it from knocking. Even the GEMS cars had swappable chips for ignition curves. The only reason they did that was for low octane countries.
Any feeling of an improvement from higher octane fuel in a 9.3 to 1 compression engine is probably just in your head.

 

i thought 93 has zero ethanol at least shell does, regardless 87 is fine, unless you asked disco mike he was crazy about good gas, i ran 87 always

 

Man I am really gonna drive you guys nuts. I run 85 in mine (I live at elevation). I put sea foam or octane booster in every now an then, but frankly, this engine isn’t worth putting high test in. In my last D2 (we lived at a little over 4k feet with that one) I did the same for over 40k miles with no ill effects. The economy is so bad, paying the close to a dollar difference per gallon doesn’t even come close to making it worth it. In my S4 that legitimately takes high test, I gladly pay it out of fear more than anything, but that thing also gets 30 mpg believe it or not.

When I did put premium in the last D2, it gave me maybe 1 mpg increase and nothing worth noticing on the butt dyno. I’m a total Disco addict, but premium in them is wasted money in my opinion.

 

Yep you'd get more bang for your $$ with a K&N Air Filter ROFLMAO.

You can ask anyone that knows me or that I've passed on the road, and I DO NOT baby the Rover V8, if it's gonna blow it's gonna blow. No Mrs Daisy cruising around at barely over 2,000RPM. I will drive my foot to the floor until the kick down cable does it's thing on a RRC/D90/D1, or the ECU know's I'm hitting the red line on a D2. Carbon? What Carbon... If 89/93 Octane was only 15-25 cents more sure use the higher octane, but over 1.00 more per gallon is just highway robbery IMHO.

The only LR V8 I always use an octane booster on or use 93 octane if it's cheap = 14CUX RRC/D90/D1. It doesn't have knock sensors so under heavy load it "could" ping. However I have my 95 D1 setup using Volvo 4 Hole Injectors, and a VW/BMW Fuel Pressure Regulator, and I have yet to ever hear it ping. She also isn't running any cats and just has straight "off road" pipes installed instead. Probably the most powerful LR and quickest accelerating LR I have to be honest.

I reset adaptions at every oil change on both the D1's and D2's (LR did that as well at the Dealership back in the day), then drive it pretty hard until the ECU learns from the baseline settings.

When I towed a D2 with a D2 using a U-Haul Dolly & a D1 with a D2 and another U-Haul Dolly the D2 did fine. Both trips were in some pretty serious hills/elevation changes throughout the trip home and stop n go traffic. Once up to speed the D2 just cruised along and handled the load of the D1/D2 behind it and the trailer just fine. I wouldn't make a habit of doing that kind of towing, but it worked for the short 3.5hr tows just fine.

 

Thanks for all of the feedback/input. I appreciate the K&N comment as I have never used a K&N on any of my Discoverys.

After about 60 miles, the throttle response feels better and my downstream cat readings from my OBD2 reader seem better. I'll be driving longer distances tomorrow and I'll have a better feel for performance, etc. BTW, I only paid $3.89 for 93 pure gas which I thought was pretty good. I might try 89 next time to see if I can tell the difference.

 

Dang, we're paying $3.89 for 87 here in PA. If you can tell the difference between 93 and 89 in one of these trucks, you might want to try to get a job as a quality inspector. The fuel whisperer. As pointed out, most places are blending at the pump to come up with mid-grades and knowing what I know about how business is done these days, I'd be surprised if anyone is actually getting what they think they're paying for.