Engine oil grade v fuel consumption - part 2

A month or so ago I posted about the increase in fuel economy on my regular Aberdeen trip after putting 5/30 oil into my Focus instead of the 10/40 that had been in it for the last three years. Normal economy on that journey is

33 mpg but with the new oil I got 36 and 38 from the next two tanks.

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Unfortunately I didn't get to go back up to Aberdeen this month again to exactly repeat the test but I did do a few hundred miles of motorway driving last week to visit a colleague in Sussex. The first 107 miles of the tank were the usual short shopping trips to the village with a cold engine which always give 27 mpg and the fuel gauge reaches the first mark at 95 miles which it did exactly this time too. The trips to Sussex were 72 miles each way over two days, mainly motorway mileage on the M25 and M23 with about 12 miles at each end on A roads. Obviously that means the engine starts from cold a lot more than on a single long trip like to Aberdeen so I wouldn't expect quite such good economy. I also ended up in a 10 mile tailback on the M25 for over an hour which can't have helped.

Results over the full tank were 382 miles using 51.4 litres giving 33.8 mpg. That's still better economy than I used to get on a single long trip. Knock off the first 107 miles of short journeys at 27 mpg (18.02 litres) and we get 275 miles using 33.38 litres for the motorway journeys giving 37.5 mpg.

So it definitely seems that the economy has improved by a considerable margin to circa 38 mpg rather than 33 mpg once the engine is hot.

Reply to
Dave Baker
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So what about installing a cooling system heater, so you start off with a hot engine? The kits are available over here now.

Reply to
MrCheerful

I've been thinking the very same thing. The economy on short trips with a cold engine is quite appaling. Less than 20 mpg for the first mile or so. I know that because I once did a full tank of only trips to the village and got 19.9 mpg. Usually though that mileage is interspersed with longer ones to Tesco in the nearby town or to a mate's house which bumps things up to mid/high 20s. In the good old days you could push the choke lever in and let it splutter a bit once you were underway but with modern engines there's nothing you can do to get it back to a weak mixture faster.

However, an engine heater means switching it on however long you need to before setting off rather than just getting in and driving off, the cost of the thing in the first place, rigging up to an electricity supply. Can't be arsed frankly although I'm quite sure it would pay for itself. I know in very cold climates they are pretty much mandatory if you even want the engine to crank over. Might be easier to have a mixture dial on the dash so you can lean off the fuel.

Reply to
Dave Baker

now there is an idea you could sell !!

the webasto heating kit runs on vehicle fuel, no power supply needed !! must be lovely when you visit someone in the winter and can walk out to a preheated car

Reply to
MrCheerful

The message from "MrCheerful" contains these words:

Hmm, what shall we call it? Well, since it'd be really used to make the mixture more rich for starting it'll make lots of choking fumes come out of the back which will upset the greens - so perhaps we should call it a Fumer.

Reply to
Guy King

Ooh, I know, I know! If it will make choking fumes come out the back, why not call it a... choker?

Reply to
PC Paul

no, call it a 'Leaner, Greener Fuel Economy Device' it would sell like mad. After all if it was just linked into the existing CTS circuit it would be quite feasible to make it so that it could only weaken the mixture, mind you then the lambda sensor would try and richen it up again, so maybe there would be quite a few bits to connect, it would certainly be feasible to construct, probably illegal to sell or use !!

Reply to
MrCheerful

Trouble is it would mean lots of jiggery pokery with the electronic bits and that's beyond me. However !!! If I remember my physics right, if you have airflow going through a tube which has a restriction in it the pressure drops. Bernooley or summat said that I think. Now call me old fashioned but if you connected a little pipe between a fuel reservoir and this restriction the airflow would suck the fuel right on into the engine. No need for electrickery or electronickery just simple airflow. Might need to calibrate it all with some replaceable fuel jets to suit different applications, stick a butterfly in there to control the airflow maybe, your fumer knob on the dash to open a cold start system. In fact I reckon it would be so simple people could even fix it themselves if it went wrong which is more than anyone can do these days if their car breaks down. I wonder why no one has thought of it before.

Reply to
Dave Baker

That's just lunacy! Think of the floods it would cause. And droughts.

Si

Reply to
Mungo "Two Sheds" Toadfoot

and the emissions will kill the children

Reply to
MrCheerful

Fuck em. All they do is hang around in gangs spitting, littering and scaring the local populace. We have dozens of the little sods in the village which used to be a nice quiet place before they infested it. Anything which reduces their number is a good thing in my book.

Reply to
Dave Baker

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