No they don’t. Long oil changes creates sludge. Narrow return passages get blocked by that sludge so oil can’t drain back from the head.
Also no. Single grade oils do not sludge less. Where do you GET this stuff?
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From the Internet. I don’t remember where now. It was some article about viscosity modifiers. They are long molcles that expand at a certain temperature and make the oil thicker. Apparently they break down with use and heat. This makes the oil not get thicker with temperature whith is bad, and if I remember correctly, they can contribute to sludge.
Well, if it is on the internet, it must be true, 
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Not to continue this but I have never heard an expert saying to modify the weight of oil used. Just some folks on the internet afraid of zero weight. As far as how long to go between oil changes, Acura says to follow the oil meter. An automotive expert say 5000 miles and forget the 10 to 20 mile intervals, and a Toyota engineer said use the cheapest oil and change every 2 to 3000 miles if you are trying to get to 300,000 miles. I just change at 5000 now or 3000 with Dino, and had no trouble getting to 500,000. So if you don’t mind, I’ll just ignore all of the conflicting advice and keep doing what I have been doing. I don’t mind the money.
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This was an issue…30+ years ago. Not now, assuming oil change intervals are honored.
So what changed? Please not something vague like “better technology”.
Oil may be better, but if we have very tight tolerances that shear the oil, then we’re back to where we started.
Right? It really seems that just keeping a conservative OCI will ensure the oil performs only as expected without relying on the continued integrity of all the modifiers, detergents, etc, right?
For me I’m doing 3750 min OCI since I drive a ton and also have lots of mountains and grades.
If you’re doing this no need for the extended performance version of Mobil1, go with the regular version, it might even be better for your engine under your driving conditions. The extended performance version puts extra components that are consumed to account for long OCI, which you aren’t doing.
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I don’t plan to get involved in a long drawn out discussion on oil but there seems to be some conflation going on in this thread regarding oil degradation.
The polymers used in Viscosity Improvers (VI) are long chain molecular constructions and subject to physical shearing. This primarily is a mechanical process that occurs where metal parts meet (think gears meshing as an example). This shearing reduces their effectiveness at providing viscosity control across the operating range of the oil. Polymer chains are not the only way to produce multi-viscosity lubricants but when used, they are susceptible to shearing.
Oil sludge is something different. It is the physical breakdown of the oil itself due to thermal and chemical interactions. What has changed? The formulation of the oil and additives to address these causes of degradation-
- The use of more thermally stable oil bases helps to offset the thermal effects on oils by reducing oxidation of the oil
- Better dispersants help to keep the particulate matter in suspension and prevent them from combining into larger masses.
- Better detergents neutralize any acids that would normally build up in the oil and contribute to further degradation.
The science of lubrication hasn’t stood still. They keep improving it. It’s not just some liquid pumped out of the ground and refined, it’s a purposefully designed mixture of various lubricants, anti-oxidants, dispersants and detergents designed to provide lubrication under adverse operating conditions…
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Thanks for the useful information.
I was reading about a car problem where a certain Toyota would develop oil sludge even though the regular conventional oil used was changed fairly frequently. What do you think was going on?
edit: I read the following article that is linked. I hope it wasn’t written by a bot! https://takeuroil.com/viscosity-modifiers/?expand_article=1 It says the viscosity enhancers do shear. I don’t know if they contaminate the oil or not.
This one? Mobil 1™ 0W-20
Despite frequent changes, some engine designs have been known to create sludge. Perhaps they have hot spots with insufficient cooling to prevent overheating the oil or they have excessive blowby that turns the oil acidic more rapidly than typical. Anything that overwhelms the oil’s ability to withstand breakdown could be at cause for premature sludging.
Of course they shear, I wrote that earlier-
When I look at the Mobil1 web site it says 5W-30 synthetic is recommended, as does the Pennzoil web site. The link you supplied was for Great Britain, is that where you are?
What does the cap on your engine say? Your owners manual?
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The problem with those vehicles was Toyota made the engine run hotter for emissions. This caused unnecessary sludging. The solution was to more frequent oil changes, or switch to a full synthetic.
Air cooled engines traditionally use single viscosity oil in the summer because they run hot and multi grade can’t handle the heat. I know some of the lawn mowers now are using 10W30 conventional. Maybe the oil has gotten better, or maybe they don’t care about longevity like they used to.
I don’t see why the same wouldn’t apply to a car engine that runs hot.
Multi-weight oil for lawnmowers has been around for decades. Nothing new. Especially if you have an engine with a pressurized oil system and oil filter. I own a 48" walk-behind mower with a Kawasaki engine that recommends 5W-30 or 10w-30. It was built in 2000.
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It is because Briggs and Stratton engineers were more stubborn than mules. Most owners of their engine ignored their insistence and used 5W30 or 10W30 because they had it around the garage. And now B&S says it is OK to use. 
As far as single weight oils handling the heat better… Poppycock. When I was racing my Chevy, I used 5W30 Mobil 1 and regularly saw 290 F oil temps when racing.
From the most famous builder of air cooled engines in the world, Porsche, and what THEY recommend be used in their vintage air cooled Porsche engines…
If you scan down the page…EVERY recommendation is to use a multi-grade oil. 10W50, 20W50 or even 10W60 depending on the model of air-cooled engine. This from the manufacturer that won 17 overall wins at the Le Mans 24 hour endurance races and countless race and class wins around the world.
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I think the old recommendation to use straight weights especially in small engines was due to several considerations at the time- the amount of oil in the crankcase was fairly small, the equipment didn’t need a wide range of operating temperatures and VIs take up volume and provide no lubrication. So, maximize the amount of oil available for lubricating purposes. Unfortunately, I don’t have any data indicating if the sump today has more oil volume than they used to provide. You can count me in the camp that eventually just poured in whatever I had around and called it a day. Didn’t seem to make any difference but not exactly a science experiment 
I recall back in the day, detergents in the oil were verboten as well. There was a small section with straight weight, non-detergent oils for small engines…
Agreed. The main advantage for single weight oil is - It’s pure oil. No modifiers. The modifiers don’t lubricate as well as pure oil. But I also believe a Full synthetic multigrade oil is better than a single grade oil. If never seen synthetic single grade oil - Only regular dino oil.
And no single weight oil meets any carmakers’ oil spec, I’d bet.
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