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Since we hijacked another thread lets start/finish our oil grade discussion here.

The question is do you use a multi grade oil (15-40 ish) like 99% of the population or a single grade for warm outside temps and why.

I like multi grades for cold starts but single grades for summer temps and IMO single grades maintain their advertised properties significantly longer, multi grades contribute to sludge build up and break down faster than single grades. Of course I do not want a single grade 40 for -10C.
 

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Since we hijacked another thread lets start/finish our oil grade discussion here.

The question is do you use a multi grade oil (15-40 ish) like 99% of the population or a single grade for warm outside temps and why.

I like multi grades for cold starts but single grades for summer temps and IMO single grades maintain their advertised properties significantly longer, multi grades contribute to sludge build up and break down faster than single grades. Of course I do not want a single grade 40 for -10C.

The highlighted part of your post is a bit bias, I still stand by my previous answer, considering real life variants:

See where your coming from Paul, but Perth is not the tropics, neither is where I am near Brisbane Queensland. Even though our summer temps can be in mid thirty's to 40+, winter temps can go down to -5.
Traveling this great land of ours bring a further need for multi-grade, last year while traveling from the "Kimberlies" to "The Red Center", temps went from 40+ to -4 over the duration of a couple of weeks (late Autumn, your Fall).

Ideally we could change a mono-grade to suit the seasons, but in reality it is far easier to use multi-grade, which it is also designed for.

Adding to that, with modern multi-grades and our 5000km oil changes (TD4.2's) the polymers have not broken down.
Also in many parts of our great continent you can get temp changes from -5 to +30, in one day (e.g. Alice Springs in winter), and I might add, it is what the manual recommends.
 

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Discussion Starter · #3 ·
I'm not following how warm outside temps is a bit bias but if I need to quantify then +10-+40 and up.

I saw some large temperature swings in Tchad but the lows only lasted for a couple of hours in calm wind. Not long enough to be a factor.

My whole point is IMO a typical 15-40 does not have much 40.....
 

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Discussion Starter · #4 ·
and no, I am not going to run a straight 30 in winter here.
 

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Yup, on the same day.

Shocking huh?

I grew up in ippswich (a coastal ish city). In winter i gets to -2 regularly and durig the day can get to 25 deg.

In the centre (of the continent), it's colder at night and hotter during the day. HUGE variations.
 

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Discussion Starter · #8 ·
Well, like the desert in Tchad I suspect the lows temps do not last for long.
 

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I like multi grades for cold starts but single grades for summer temps and IMO single grades maintain their advertised properties significantly longer, multi grades contribute to sludge build up and break down faster than single grades. Of course I do not want a single grade 40 for -10C.
Multi-grade is good for cold start and also for summer temps! The viscosity of multi-grade oils changes with temperature and different components of the engine are at different temperatures during normal operation. This means that the multi grade oil would have a higher viscosity at the piston ring zone, which would result in lower oil consumption.

Also, multi grade oils have higher additive packages (API CJ-4) than single grade oils (CF).
 

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Discussion Starter · #10 ·
Morning CARIB, we could debate this a bit. Multi grade oils promote oil consumption. An engine will use more oil if it is a multi grade and the consumption will increase the more used the oil gets. This I know from practice.

I wasn't aware multi grade oils have a higher additive packages other than the polymers that make the oil a multi grade. Is the increase in additives to counteract the increase sludge?
 

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We could debate the oil consumption issue! Most high quality multi grades do reduce oil consumption because the viscosity is higher at the ring zone. Lower quality multigrades, the ones with poor quality viscosity index improver additives, would result in higher oil consumption because of shear down of the VI additive. When this happens, the oil suffers a permanent drop in viscosity.

As far as I am aware, none of the oil companies formulate a mono grade diesel engine oil with an API quality higher than CF. The reason for this is due to the fact that these have higher oil consumption than multi grade oils. When the oil is burnt in the ring zone, the metallic additives form a very abrasive ash which increases engine wear and the oil will not pass the higher API classification tests. Of course, these higher API quality oils are designed for the newer engines and have more additives to prevent wear and sludge formation.

Engine oils have detergent and dispersant additives which are supposed to clean the metal surfaces and keep the contaminants in suspension until they are removed by the filters or when the oil is drained.

Sludge is normally formed in the low temperatures areas of the engine. I wonder if the cold climate at this time of the year in Canada, I know because I am currently on holiday in Toronto, is contributing to the increase in low temperature sludge that you are experiencing.
 

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The only factory recommendations for mono grade that I have seen were for air-cooled engines like Briggs and Stratton (like most people here I always used 30 grade for 4C to 40C) but I just bought a new mower and even they now recommend a 10W-30 synthetic with mono 30 grade listed as "an acceptable substitute". Air-cooled aircraft engines used to use mono grade but I don't know if that is still true. I believe that the VI improvers in multigrade have themselves been improved over time and synthetics need less or no VI improver.
 

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Discussion Starter · #14 ·
Not much time right now.

CARIB, there is a serious flaw in your logic. Nobody vacations in Toronto this time of year.......I am about 4 hours driving to the east of you.
 

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Just my 2cents, my Petrol GQ 1990 has been on gas since 30,000km and has been run on Pentrite Gas Oil (multigrade) changed every 5000 . I'm the second owner , the 1st one did 400,000 towing a 30ft van down in Victoria. It now has 513,00 kms on it and the only oil it uses is what is leaking out the front seal (must fix that sometime)
 
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