Synthetic Oils

[ShipFixer]

I mostly run synthetics for the gas mileage increase. Not so much for longevity.

how much difference in mileage do you get?

I have not tried it on the pathfinder yet, just bought it on friday (have a little over 300mi on the OD). On my 2001 ford ranger I changed everything from engine to rear diff over and picked up 4 mpg. So from 16 mpg to 20mpg highway. I own my own company so i get Amsoil at cost, that is the main reason that i run it over other synthetics but i would imagine that it is not just Amsoil that gives good MPG gains other wise they would be the only ones selling synthetic

coming from the BMW world (which i have not completely left since that is what i work on everyday) there is little to no gain going from stock oils to Amsoil since BMW's come with synthetic in them already.

I call shenanigans If you saw any kind of mileage increase like that it's due to some other problem you inadvertently fixed, like contamination, or a change in other conditions. The work lost to working the oil is directly related to viscocity (see the Raimondi-Boyd formulas and charts); there is no efficiency or "mileage" advantage to a synthetic over a conventional oil of the same viscocity, assuming they test about the same (and most of them do). They claim it, but it's nonsense. The only thing the sliding or planing surfaces care about is viscocity.

In fact, since viscocity decreases over time as the oil breaks down, you should have higher mileage with older oil rather than lower.

There are some other concerns like fuel dilution, combustion byproduct contamination or even solid contamination that come into play with really old oil. But in general your engine should be working harder against new oil of the same grade.

As for Amsoil, it's often called Scamsoil. It's not quite that bad but it's not that awesome either. They have a habit of taking tests that are more appropriate for, say, ball bearing grease and pumping them up as proof that their oil is better. It's been a few years since I've had to look, but the reality is that they're not testing better than Mobil 1 in more oil-specific tests.

In the end though, with this kind of engine I don't believe you can go wrong with just about any kind of oil so long as you change it regularly. I generally use synthetic for the resistance to sludging, but at the same time I'd be just fine doing conventional.

If I had some kind of BMW engine that specs something like a 0W oil (which tells us something about the bearing design assumptions) and I was really concerned about viscocity breakdown, then I'd be much more neurotic about only using synthetic...

[skinny2]

Toyota is now using a 0w-20 synthetic in most (all?) of their engines. Free service for first two years...at 10k intervals. I did the first one my self at 5k just for good measure...ended up buying the oil from the dealer.

[ShipFixer]

Toyota is now using a 0w-20 synthetic in most (all?) of their engines. Free service for first two years...at 10k intervals. I did the first one my self at 5k just for good measure...ended up buying the oil from the dealer.

There is a potential downside. Lower viscocity oils will increase efficiency (we're talking a tenth or two miles per gallon). But you're reducing the thickness of the fluid layer and increasing the "eccentricity" of the bearing (basically the distance between the center of the inner shaft from the center of the outer part). In order to score higher on CAFE, automakers first reduced the viscocity of the engine oil in new cars while keeping the specifications the same. So the test rigs would get that extra gnat's ass of efficiency for the official mileage ratings, but the end users would put 10W-30 or something in it and protect the engine properly with the oil viscocity the bearings and other things were designed for.

Then the government kind of got wise to this game. So to meet the same CAFE standards, the automakers specced the same viscocity oil that they were now loading them with.

Viscocity engine and bearing design go hand in hand. So you can have a bearing designed with lower tolerances for a light oil and a bearing with higher tolerances for a heavier oil and functionally they're the same.

So when you put 0W-whatever in a BMW and the bearing was designed around it, that's one thing. But when Ford or other makers started speccing lower visocity oil for engines that had not changed, welll...look out.

It's not like your engine is going to explode or something. But dropping from the highest viscocity it's rated for to the lowest can increase the wear particulate volume by almost an order of magnitude. So when they drop to something really low like a 0W-20 and they were running 10W-30 with the same engine before, you should do some head scratching.

They are basically picking their CAFE standard and a minute mileage increase you won't even see in real life while increasing the end user's total cost of ownership by decreasing the lifespan of the engine.

Of course, it's not like anyone told you that in the open and gave the consumer the vote

[ShipFixer]

Oh, forgot to ask, what is "service" at 10K miles? Does that mean the oil isn't changed until then?

The general rule is 1K miles per quart of oil, determined not by viscocity break down alone but mostly acidity and other contamination issues. I believe some automakers have installed sensors or at least a predictive algorithm based on driving habits that tells you when to change the oil based on conditions, but, I think I'd still change it every 1K mi/qt.

[skinny2]

Yes they're recommending oil change at 10k (when using synthetic) and in wife's case (Sienna) it holds 7.5 quarts. Honda/GM use the driving condition "sensor" but Toyota does not. Most of those systems are calibrated for conventional oil (5w-20 for Honda). My wife's previous Honda Odyssey typically pinged her for an oil change around 6,500 miles and using conventional that still seemed to be quite conservative. I had a couple oil analysis run and Blackstone recommended 8k easily.

I'm not sure I buy into the 1k/qt logic, particularly for synthetic. Oil analysis is the only way to know for sure and I've performed them on most of my vehicles if I do extended drains. My VW TDI had 5 quarts of synthetic and the factory interval was 10k. Testing showed that was VERY conservative. Car had 250k miles when I sold it with no problems at all. My Dodge below is on 10k intervals of Rotella T Syn and has also tested perfectly fine with over 200k (heavy towing) miles on the clock.

In the case of my wifes car...she'll never keep it passed 100k miles so I'm pretty sure we could run it on monkey piss and be just fine. Not sure if we'll go with the 10k interval or not. I changed the oil myself at 5k just to swap the factory oil. Toyota originally was calling for 5k intervals on these (conventional) so obviously I'm skeptical. Theoretically it should be fine at 10k on synthetic though. If I change it early it would just be to help out the next owner and maybe get a small bump in resale. We did a private sale on her Odyssey and the buyer was impressed with my maintenance records. Certainly got top dollar for it so it may be worth it...just depend on the buyer I guess. I've sold other cars the buyer didn't even ask about service records.

[ShipFixer]

1K/1qt is from the test engineers at Southwest Research Institute, the largest diesel test lab. Viscocity and fuel dilution are most likely fine at 10K. But acidity from combustion byproducts may not be and is not always tested. Did your tests include that?

Condition-based oil changes as is done with seriously big engines is of course the best, but most of us don't have an oil test facility handy. There's also a financial consideration where its worth it for a diesel with 45 or many more gallons in the sump and maybe not for a Sentra with 2.8 quarts. I'd rather not test my oil all the time, so of course it is a little conservative.

I've driven vehicles 10K in between because I get lazy and don't care, but...not taking chances in the Pathfinder. We have too many failures as it is, some of which are touched by engine oil and involve corrosion/possible acidity issues, such as the radiator. I'm not putting the best stuff in (it's a truck driven conservatively after all) but I am changing it all regularly.

[found]

oil testing is about $25, i do it every other oil change to monitor bearing issues (some BMW engines are known for it s54 to name one)

[volvite]

I'm going to bring this thread back to life. I've been using Mobil 1 in my Pathfinder since I bought it, Feb 2011. I just picked up a used 2006 Mazda Speed6 to replace my 91 Honda Prelude. On my Mazda forums, they swear by Rotella T6 5W-40. They claim...

"Shell Rotella® T6 5W-40 provides unsurpassed protection against shear-stability degradation, compared to the leading competitive API CJ-4 5W-40 products. An extremely shear-stable product helps maintain consistent viscosity and oil pressure in the engine.
YOUR PROTECTION - OUR EXPERIENCE"

I know there has been talk about our Pathfinder's timing chains wearing out fast and needing to be replaced.

Has anyone tried this oil before? Will the 5W-40 hurt our pathfinders? I believe it calls for 5W-30, so I don't think it would hurt our motors.

Thoughts?

[smj999smj]

The issue isn't so much that the timing chains are wearing out and needing to be replaced. Supposedly, the links of the upper chains were too sharp and cutting into the plastic tensioner "feet." Nissan updated the secondary chains (although I compared the old and new chains and really didn't see much difference, so I'll have to take their word on it) to correct this issue, which is why they instruct to replace the upper chains as well as the tensioner feet. It was never an issue of lack of lubrication. While 5W40 probably won't hurt any, I'll stick to using 5W30.

[volvite]

SMJ,

Thanks for the clarification. I think I'm going to have an Used Oil analysis (UOA) done on my Mobil 1 when I do an oil change next and see where we stand. I then might try the rotella and see what it does.

[smj999smj]

I've been using Walmart's Syntech full-synthetic 5W30 for years with no complaints. It's made by Royal-Shell, the makers of Rotella, and the price is tough to beat at $17 for a 5-gallon jug. NAPA also has an inexpensive full-synthetic which is made for them by Valvoline. Right now you can get 5 quarts and a NAPA silver oil filter for $19.99.

[volvite]

SMJ,

I'm not too worried about cost, more about ensuring my engine has the lubrication and avoid costly repairs. Like I said, I've been using Mobil 1 with lucas and I don't hear or see any problems, just on the look out for something that might be better.

[akley88]

i recently just put in royal purple. there has been no major mileage difference that i have notice, but the engine sounds and feels a little smoother.

[cossey00]

I've just ticked over 160,000 miles on my 2008 2WD SE. Used Mobil 1 for the first 100,000 miles then changed to Castrol's Edge Titanium. I do changes between 6-8000 miles and am just starting to have oil analysis done. I use fully synthetic all around - Transmission & Diff included every 30,000 miles religiously and do coolant every 30,000 as well. So far this truck hasn't missed a beat. Love it.

[skinny2]

I've just ticked over 160,000 miles on my 2008 2WD SE. Used Mobil 1 for the first 100,000 miles then changed to Castrol's Edge Titanium. I do changes between 6-8000 miles and am just starting to have oil analysis done. I use fully synthetic all around - Transmission & Diff included every 30,000 miles religiously and do coolant every 30,000 as well. So far this truck hasn't missed a beat. Love it.

Good to hear. Mine has performed very well now approaching 100k and I'd love to get another coupe years/60k miles out of her. I don't think there's much on the drivetrain that's really a weak point for these. I've not seen many (any?) transmission failures that weren't related to radiator failures and not sure I've ever seen someone here lose an engine. Some of the electronics might cause grief down the road which is what concerns me and no amount of maintenance can help that.