Another Vvti Oil Question.

[fastbob72]

Happened to come across this post on HonestJohn and wondered what you'se might make of it ??

"I have two Toyota's one is a Carina E 221,000 miles, it uses no oil between changes.

The second is an Avensis 1.8vvti Automatic with 96,000 on the clock. The engine has been using oil at the rate of 1 litre every 700 miles.

On another forum I read of a cure. The person who posted the reply claimed that by using about 4 tankfulls of High Octane unleaded instead of ordinary unleaded the problem improves.

As an engineer of 50 years I was not convinced about this but then I though maybe the detergents in the High octane may be better that the ordinary unleaded & may clear sludge or crud from the oil scrapper ring groove, so I tried this out.

Well, 4 tankfulls of high octane later, the oil consumption has dropped to 1 litre every 3000 miles. I am going to use one more tankfull then revert back to ordinary unleaded to see what happens.

Give it a go it may work for you."

Now,like the guy above,to me the notion of filling with 4 tanks of Super Unleaded seems both pointless and unnecessarily expensive.In itself running on higher octane fuel makes absolutely no difference unless your engine is set up to benefit from it.The thing all these boy racers don't seem to realise is you don't get better performance by filling with 98 octane fuel.All it means is that while you run it you're engine has a higher tolerance to knocking but unless you're knock sensor is regularly altering your timing because you're engines often on the threshhold of knocking or you adjust your timing to make use of the higher octane fuel then it'll make absolutely no difference to the way your engine runs !!!

Therefore,if it's true that running 4 tanks of Super Unleaded can improve your oil consumption on a 1ZZ-FE then it's not the octane rating of the fuel that's improving it but something else,possibly superior detergents and additives like the poster suggests.

If that is true then isn't there an fuel or oil additive that could have the same effect without actually having to fill up with 4 tanks of more expensive fuel ??

What does anyone/everyone think ??

Personally,I'm highly sceptical but it's an interesting idea !!!

Has anyone else heard of running higher octance fuel improving oil consumption ??

Bob.

[Flakmann]

Hi Bob,

An interesting post; Are you back on ordinary unleaded yet? and if so, has oil consumption reverted back or near to 700m/litre?

What is the significance of the Nr.4 in 4 tankfuls; did you dip the oil after 1 tankful etc? ie, would oil consumption still lessen after say 6 tankfuls?

[sproutdreamer]

I saw the post about use of high octane fuels a couple of years ago. The principle as I remember was that the higher detergent levels in the high grade fuel was helpful in keeping the ring grooves from blockage with oil solid deposits. I cannot rember exactly how much oil I was using at the time but it was a concern that it was starting to burn oil after only about 50K miles.

Anyway I did start using the high grade of unleaded and my oil consumption dropped to 1/3rd. However unfortunately at the same time I made a couple of other changes. I filled the oil 10mm above the full line to help the oil not get overheated ( factory mod with rebuilt engine has a higher dipstick line I understand) and I started using fully synthetic oil.

So it could be any one of these things or perhaps a combination of al;l three that improved my oil consumption. It does make sense to me that if the problem is small sump capacity causes the oil to overheat then poor piston ring engineering could cause gumming of the rings then increasing the oil capacity may reduce the oil temperature a little, use of synthetic oil makes sense to withstand highish temperature of the oil and more detergent in the petrol to keep the ring grooves cleaner. All makes sense to my tiny mind and worked for me for the last 15k miles. I make a 600 mile round motorway trip about 10 times a year. It was using about 0.5 litres of oil for this trip so perhaps 1200 miles per litre with absolute repeatability, this dropped to using about 0.5 litres for three of these 600 mile round trips carrying the same load for the exact same trip at the same average speeds.

[Flakmann]

ok, I take the point about using a good fully synthetic oil and increasing the oil capacity to keep it cooler (apparently a deeper sump is available - same dipstick); but I think member fastbob would like to know if adding a bottle of some kind of additive to ordinary unleaded now and again would be equally as effective as buying gallons and gallons of high octane petrol.

As yet, I haven`t found a good low mileage early automatic Avensis, but it`s good to read these experiences.

[fastbob72]

Thanks for your responses flackmann n sproutdreamer.Your car doesn't sound like it was that bad then initially sproutd as my owners manual says that oil consumption up to 1 litre/600 miles is acceptable (which would cause me a fair bit of concern in any other car !!!).Anything more than 600 then there's a problem so using 0.5 litre/600 miles would seem to be ok according to Toyota and dropping to 0.5/1800 is very good.

I was really just interested to hear if anyone had tried it,hear opinions aswell.

I mean does super unleaded have higher detergent levels,I'd have assumed it'd be pretty much the same but I could be wrong.As for adding oil additives,like for example Redex to the fuel I suppose it can't hurt.I know I've taken the plugs out on older engines,poured a measure down each bore and left it for 30-45 mins before turning it over (remember to cover the plug holes or you'll get splattered with oily redex and carbon.lol) before putting the plugs back and running it.

Seemed to help dissolve carbon maybe it'd help ungum the rings,if you were having problems !!!

I've not tried running mine on Super unleaded as I'm not experiencing any oil issues so far and I'm not convinced it alone will be that effective.Last time I topped the oil up,to the full mark on the dipstick,I zeroed the trip meter and I'm going to check it every couple of days until it's used a litre.That way I can get a good idea of my oil consumption.

Then I'll change the oil and filter,refill with fully synthetic as I've been doing anyway but top up a further 10mm on the dipstick and see what difference that'll make.Also I've been keeping an eye out for a 7A-FE at the scrappies so I can remove it's oil cooler,hoses,sandwich plate before the filter etc so I can adapt it to fit mine !!!

A new block would be better though :)

[t-spiritpete]

It's just my opinion but I think it unwise to run an engine until it has used1litre of oil as lack of cooling will make matters worse, why not just use 1/2 litre and double the figures. It's well known that the vvti didn't have enough oil in the sump in the first place.

For what it cost I would try the high octane fuel trick anyway, nothing much to loose really.

Pete