Low fuel in the T8

[Milliner]

Anyone else with a T8 find that the hybrid system defaults, most of the time, to the petrol motor when low on fuel (orange indicator - 30miles or less), even though it has a full charge?

Seems counter-intuitive to me when you'd want to be saving fuel rather than using it. I can only assume there's something going on with the hybrid system that needs it to be set up this way?

Unless it's just my car... (XC90 T8 MY17 btw)

[Neil S]

Yes, same here. The petrol range is also wildly inaccurate in that 30 miles can often mean 10. The number of times I've had to crawl along the inside lane of the motorway hoping to reach a service station is getting ridiculous.

[Milliner]

Could that issue be that the range is only a guide based on previous mpg?

I tend to do far more short journeys than long these days, so I'll sometimes set off down the motorway with, say, 90 miles range, only to find I still have a 90 miles range 3/4 hour later! It recalcs as the mpg improves (or declines in your case).

[encroute]

Not in a T8, but this range thing is the same for me.
Definitely based on current/recent consumption

Left Central London with 100 miles to refill, and 10 minutes after I hit the motorway (20 mins later) recalculated to 160 miles to refill.
Quite common - V50 was the same.

[Neil S]

I haven't had a car as bad as the T8 in years. I have to fill up every 250 miles on the motorway and ignore both the gauge and predicted range. The size of the tank often means I have to fill up twice a day. I could do 700 miles on a tank in the X5 and the predicted range was consistent and reliable. On motorway journeys the electric charge is pointless.

[MaDProFF]

I have not noticed anything wrong with my 2019 XC60 T8 although I do not let the petrol get that low in the tank that often.

Only once, it went down to 40 miles range left, it seemed to keep in track , with what was left on the fuel gauge, never seem to make any difference to using the battery, though I do use it in individual mode.

I did have an issue with the battery gauge, and range when the last software update was carried out a month ago odd, I took the car back after a few days, and then another trip for them to re-code that portion of the update, the gauge/range has worked since, and waiting for a newer update.

[Milliner]

Originally Posted by Neil S

I haven't had a car as bad as the T8 in years. I have to fill up every 250 miles on the motorway and ignore both the gauge and predicted range. The size of the tank often means I have to fill up twice a day. I could do 700 miles on a tank in the X5 and the predicted range was consistent and reliable. On motorway journeys the electric charge is pointless.

I believe the tank is bigger in the current model. It was a bit small for long distance.

[Director76]

Originally Posted by Milliner

Anyone else with a T8 find that the hybrid system defaults, most of the time, to the petrol motor when low on fuel (orange indicator - 30miles or less), even though it has a full charge?

Seems counter-intuitive to me when you'd want to be saving fuel rather than using it. I can only assume there's something going on with the hybrid system that needs it to be set up this way?

Unless it's just my car... (XC90 T8 MY17 btw)

Yes - I posted my theory on this in another thread. I’ve only experienced it once, trying to do a day pottering around on pure with full battery. Normally easily done with no ICE at all, but in this instance low fuel light was on and ICE kept cutting in even with nearly full battery and on pure. So much so it felt like the car was faulty.

My thought is that low fuel disables the auxiliary fuel heater and thus the car triggers ICE to provide cabin heat, battery conditioning heat etc as necessary.

Whether this is just a default (but counter logical!) control system philosophy (as it would make sense to preserve fuel by not using the ICE if fuel heater can be used instead) or intended because consumption by the fuel heater is not recorded and that this could skew any residual range estimates - I have no idea, but it definitely does it and normal service was resumed after a fill up.

I’ve also nearly been caught short a couple of times in range and so now never let it get low except on a local journey - 30 miles can turn to 10 and zero in a flash on the range, particularly on motorways.

I usually use pure to get from home to fast road - drop it on hold for the motorway run and then pure the other end. This also saves some emergency electrons if you end up having a fuel crisis!

[MaDProFF]

@director76 seems reasonable your consumption that low fuel in tank, may disengage aux heater, thus cutting in the engine etc. I can only assume that heat for the cabin can only be generated from the engine running.

I do think the Fuel used by the AUX heater is recorded by Range and fuel tank, and MPG reading, as when I get in the car after using pre climate and aux heater is still running, when I turn on ignition I instantly get an MPG reading of a certain amount, (sure it varies)

As I posted earlier MY19 I ran the car pretty low the other day with 40 mile left on range, and way less than a 1/4 of a tank, and had no issues at all, the range was constant down to that point, and still changed with varying speeds, and electric was running run when I wanted to use it.

Could be an issue with older than MY19, and as others have stated there is a bigger tank on it.

I must admit still not happy that there is even an AUX fuel Heater on the T8's for UK models, it seems counter productive, especially for pre heat when connected to the power supply, filling the garage up with fumes

[Milliner]

Originally Posted by Director76

Yes - I posted my theory on this in another thread. I’ve only experienced it once, trying to do a day pottering around on pure with full battery. Normally easily done with no ICE at all, but in this instance low fuel light was on and ICE kept cutting in even with nearly full battery and on pure. So much so it felt like the car was faulty.

My thought is that low fuel disables the auxiliary fuel heater and thus the car triggers ICE to provide cabin heat, battery conditioning heat etc as necessary.

Could be, although I'd have thought the dedicated Aux heater would use a lot less fuel on that single task than the ICE which is also pulling the car along. It would make sense to me to leave the driving to the electric engine where possible as I assume if you did run out of fuel, the electricity left in the battery would then be no use at all.

Obviously, the answer is fill up with fuel, but I'm just curious about what's going on that it's set up this way!