I think I posted this somwehere but perhaps it didn't make it. Reset the trip odometer when you fill up, drive until empty, and then fill the tank. Now you have miles from the odometer and gallons from the pump (second fillup). Usually my mpg is around 15.

 

the Disco has an electronically self-retarding fuel management system. If you use anything less than the required premium fuel, the truck literally reduces the operating performance to compensate.

 

At boston4... As I mentioned before, the trip odometer is not accurate, nor is the speedometer. Nor is the OBD2 port.

If you want accurate you have to put a tiny bit of effort into it, use a gps or google maps and determine the actual miles. Your truck could be off by as much as 15%.

A 15% difference over 125 actual miles is the difference between 15.6 mpg and 13.5 mpg on the low side, or 17.5mpg on the high side.

The way these trucks suck fuel you might as well know the actual factual truth of the matter. Don't rely on faulty data when doing your math...

 

Still, when you compare with the same equipment, you should clearly see a trend.

 

Pre-detonation gets detected by the knock sensors and compensates with the timing which reduces power. It’s the same question with any car requiring premium (although Rover compression is right on the low end), am I hurting my engine using fuel less than recommended. Someone from the UK can chime in but I believe their gasoline is premium as the normal with 95 octane so using 87 octane in the US could be problematic. At higher elevations the air is thinner so you can get by with lower octanes.

 

@Jwehking 91 in North America ,they measure octane differently over there - if I recall correctly there are 3 main methods and they all give a different number for the "same" octane level

 

Interesting - my speed usually agrees (within 1-2mph, so ~3%) with GPS speed, but I have stock tires/suspension. Is this a common problem where the Speedo is inaccurate or is this just a consequence of wheel/tire mods?

 

The 03/04 LR's that went around the world with Mobil1 stickers all over them used the crappiest gas on the planet in 3rd world countries and I've seen at least 2 of those original vehicles still on the roads today.

Put whatever you want in your LR, but trust me when I say this, using 87 octane fuel is NOT going to kill your LR. It's like the famous spark plug brand/type or oil brand/type/weight debates = everyone has an opinion.

Driving your LR like Mrs Daisy (no matter what the octane fuel is being used) will build up carbon deposits quicker than you can imagine. I've torn engines down on low mileage LR's with say 45K that were babied in town probably idling a lot, and never reaching 4,500RPM's and the engine was completely full of carbon deposits!! Then I've torn down high mileage LR's with say 150K on them which were not babied, pushed the RPM's to the max, and they ran whatever fuel filled the tank, and the engine looked very good inside.

The LR techs back in the day would take a poor running D2, and leave it in first gear. They'd let it tach up until it hit the rev limiter. If you looked in the rear view mirror and couldn't see the car behind you = carbon build up, and the tech would inform the customer the D2 needed a specific LR fuel treatment to try and break up the carbon build up. The techs would drive it like they stole it, reset the adaptive settings, and send it on it's way. If it came back and was still running poorly they'd tear it down, do a valve job, HG job, and charge the customer a pretty penny. However they never told them to just drive the darn LR like they stole it or like it was a rental car lol.

I am not kind to my V8's and by that I mean I tach them all up pretty high until it shifts itself. I DO NOT let off the gas when it reaches 3K and let it downshift. 25+ years of LR's and I've yet to have a single issue from what octane fuel was used. Sure HP might not be up there, but you loose all hope on that once a lift, bigger tires, metal bumpers, a rack, aux lights, and a winch are added.

Biggest thing to keeping a LR alive and on the road = frequent oil changes, keeping it running cool, and checking on your fluid levels on a normal basis. Drive it like a Honda and going 10K on oil changes, and never open the hood except maybe twice a year = she's gonna look really nice parked in your driveway.

P.S. Last weekend I pulled a 35ft camper 40 miles on 87 octane fuel at 50MPH lol thanks to Tropical Storm Beta. 4.0L V8 ran flawless and I got the camper moved for my good friend and out of the way of Beta's Storm Surge.

 

Best is correct, Nobody ever said low octane was going to "hurt" the truck... The timing retardation is a built in factory feature!! It is designed to be able to operate on even the worst fuel just in case you are in BFE somewhere and the only available gas is out of 2 litre coke bottle.

Of course running on cheap fuel comes at a cost, as others have said. You retard the timing you lose mpg and hp, so what you save in cost per gallon you lose on the road. Unless like Best says in TX where premium is really $1.00 per gallon more than regular... Which would change the calculation for many. Here in Seattle it's the usual .20 to .30 more unless you go to some of the inner city stations where premium does cost more.

I'm sure there are other factors at play too, The loss of hp in a 4.0 may not be as noticeable... I don't know, never drove one. Big tires and heavy accessories will cost you more performance than cheap gas will lose you, but then again maybe premium might help. It is up to you and whether you are happy with how your engine performs.

 

the "italian tuneup". I do that to my truck on a weekly basis when I was still working. Going home there was one light just before a short stretch of state highway where the cops could not hide (it runs across some marshes with a Jersey barrier in the centre so they could not turn around) and I would floor it from the light and keep it there till about 80ish. Yes, she would throw some black smoke, but run much better after that.