Synthetic Oil Question

[daverami]

Hi all,

Searched around and read several posts of syn oil and probably missed a lot too.
I have a of question for those of you that use syn oil.

What are the benefits of running syn oil? My last three Toyotas, an 84 pickup, 85 pickup, and an 88 4Runner (wish I still had it), all ended up with well over 100k miles, almost 200k on the 84 pickup. I changed the oil (dino) and filter regularly, tried to do it every 3k, but sometimes spaced on it, and went to 4000. Kept up on all the PM too. Never had any problems, and they never really seemed to burn much oil as the mileage piled up.

I know the lubrication is better and you can go longer between changes, but what else am I missing?

Thanks

 

[Pskhaat]

I know the lubrication is better and you can go longer between changes, but what else am I missing?

IMNSHO that's basically it. It works out cost-wise for me to do synthetic, in fact I only change my oil once a year in my cruisere and then I use the used syn oil in my commuter car (200k runs great) twice a year.

 

[outsidr]

Other than what you mention, cost can work out to be less with interval increased, you could also argue for less environmental waste impact of used oil since total volume used is reduced, as well as the source for many synthetics is renewable...

 

[madizell]

100,000 to 200,000 miles on a motor used to be unheard of. Not that rare these days.

another benefit of synthetic oil is that, for a given viscosity range, synthetic has a higher degree of pumpability. In other words, it may have the viscosity "rating" of say 30 weight, but it pours more like 10 weight. This gives you faster oil distribution during cold starts, and a lot less engine drag at all times and all speeds and all temperatures. If you live in a cold climate, this equates to the ability to crank your motor more easily at low temperatures, giving faster starts, less demand on the battery.

Synthetic also has a high film strength, and a tolerance for higher temperatures, so it more readily survives temperature transients seen during high stress off road use, or load towing.

I use synthetic oil exclusively and have done so for something like 15 or 20 years, in engines, transmissions, T-cases, and differentials, unless the transmission specifically demands a special oil, as does my NV4500 in the CJ.

 

[ntsqd]

Think I got this link from somewhere around here, and recently too.

http://63.240.161.99/motoroil/

I'm not sure that I buy into absolutely everything said, but most of it seems logical and is reasonable.

 

[daverami]

Thank you guys for the info. I think I may end up going the syn oil route.

 

[AndrewP]

I like synthetics and use them in almost everything, but there are limits.

In a new vehicle, it makes sense to put the synthetics in early and enjoy the maximum benefits over the life of the vehicle.

If you have an older truck with a bunch of miles, switching to synthetics makes no sense. The wear you are trying to prevent has already occured and conventional oil works perfectly well.

Let me give an example. I bought my FJ60 with 160k miles. It's had conventional oil all it's life, and still gets Delo 15w-40 now at 220k. I can't see a convincing argument to use synthetics. I did swap in a new 5 speed tranny at 200k, and it runs all synthetic as does the rebuilt t-case. The 80 and my wife's Sienna get synthetics, since the've used those since new. My son's beater Nissan gets whatever is sitting around the garage-I mix brands, weights synthetics, Delo--literally whatever is handy.

The one compelling argument to use synthetics, is if you live in a very cold climate, where the low pour points of the synthetics will be a major advantage even in a winter beater car.

Summary, there are marginal benefits to synthetics, but they are significantly more expensive. You can lower the effective cost a bit by increasing the change interval to say 5K miles (more is OK too). Only you can decide if that cost/benefit works for you.

 

[Funrover]

Reasons I use Syn:

Longevity - The oil gets into areas faster. When it gets cold here the oils is quicker into all of the needed areas. You don't have the harsh start ups. There is A LOT less friction metal to metal. The increased lubrication during the winter is honestly enough.

Cleaner - the oil itself is a cleaner product for the engine

Stress - there is less drag on the engine components

My family has switched and won't return. We don't sell a car till it has at least 250K on the clock. The last few years we have sold 4 cars. They all still had compresion in the "NEW" range. Now we are also serious about maintaining all of our cars. For my dad he does 3000 miles every 2 weeks, this is a quick way to rack up miles. The synthetic actually gave him a little better MPG's ( but that was switching to every syn fluid and it was a SMALL gain).

 

[Grim Reaper]

I figure its about a wash money wise. I have gone to 6k change intervals with the intention of doing 4-5K trips and it saves me from having to sop for a change.

My 86 4runner is rebuilt end to end and now that the break in's are over its on Mobile1 synthetic. I'm getting up to 24mpg on the flat running 33x12.5'0s better range of temps and especially on the high end. little 4 bankers driving all day at 3200rpm are a little rough on oil temp wise.

My 454 powered Burb with 7k behind it on the hitch can easily get the oil temp in the pan (and I do have a temp gage on it) up to 300F if I sustain speeds of 70+ even with the oil cooler. Anything I can do to be able to handle that sort of heat and get rid of it is a plus. That 454 is HUGE (and I had 2 K5's in the same body style so I know how much bigger it is) and fill the whole engine bay giving air flow problems through the radiator.

I can tell a difference on cold mornings on both trucks between Dino and synthetic. The 4cyl especially doesn't feel as labored as its getting up to temp.

For whatever reason GM has the ECM programed to High idle the 454 (I assume to get the cat up to temp) and that booger goes to a 1800RPM idle when stone cold. I feel a little better about the synthetic under those conditions.

 

[daverami]

So, if you go the syn route, you just follow the manufacturer's recommendations for viscosity, depending on your use. Just use the syn oil instead of dino. If your supposed to use 5W30 for instance, you just use syn 5W30, same for the gear boxes and such. Is that how you determine what to use?

 

[Pskhaat]

Yep just use same viscosity rating, although I will say I will at times happily use 15-50 syn in my Cruiser where I would not do so with 20-50 conventional.

 

[madizell]

:iagree: I would note, though, that it isn't necessary to use heavier oil in a synthetic than you would in petroleum-based oil. You may if you wish, but only if the same reasoning that drives the change would apply also to petroleum, i.e., older engines, low oil pressure when hot, colder or hotter than normal ambient temperatures, extended heavy off-road trip, and so on. The fact that synthetic oil may be physically thinner looking than petroleum oil when at room temperature does not mean it is not heavy enough to do the job for which it is rated when at operating temperatures.

 

[DaveInDenver]

If you have an older truck with a bunch of miles, switching to synthetics makes no sense. The wear you are trying to prevent has already occured and conventional oil works perfectly well.

I dunno, a lot of the reasons why synthetic lubes are good for young engine holds true for older engines, too. I guess not if the engine has one foot in the grave and is leaking and burning oil, but you're on borrowed time anyway. I don't think it's a question of age but rather condition. If the engine is in good shape, then it will benefit potentially from synthetic. Switching a 150K mile old engine might mean only marginal increase in life because the cylinder hones are already worn and out-of-round, that's true (although switching could slow down the wear). But you could increase your mileage over the rest of its life, which if that's a few years more could be significant. Anyway, I understand what you are saying, but I think you can see a lot of benefits to using synthetic in any event. Lower friction, better shear resistance, lower operating temps, faster lubricant transport, less burn-off and sludge, etc.

 

[ntsqd]

One of the concepts that link I posted repeatedly mentioned was that oil doesn't thin with heat, it thickens with cold. Seems trivial, but it is an important distinction.

Where that distinction rears it's head is on a cold start. Dino oil thickens more with cold, per degree, than does synthetic. Thicker oil is harder to pump. That means that the bearings starve for oil longer with thicker oil. I seem to recall reading that Scott went to what seems like an outrageously thin oil for the trip North. There's method behind that seeming madness.

Another point frequently made in that link was that an engine at operating temp only needs, at most, 10 weight oil. Putting in a thicker oil (say 20-50) drives the pressure up, but what it really desired is not pressure but flow. Increasing the pressure this way results in lowering the flow.

 

[AndrewP]

Well, just keep in mind that Haas dude is not a lubrication engineer and his piece there is opinion only.

I choose operating temp viscosity (the 30 in 10w-30) based on the Toyota recommendation for my engine in Australia. The USA recs are compromises with the government that may allow for slightly better fuel economy at the cost of lower operating life. Both the 60 and the 80 recommend 10w-40 or 20w-50 in these vehicles in Australia. Since my summer operating temps are similar and the winters where I live are mild, that's roughly what I run, thinking Toyota knows more than Senor Haas.

Based on published oil analysis, the 1FZ motor does especially well on Mobil1 0w-40. That's almost always what I run in the 80. It also does well on Mobil1 15w-50, again based on published oil analysis and I do run that in the summers. My 60 usually has Delo 15w-40 in it, (though for this winter it's had Rotella Syn 5w-40 as an experiment) and my 40 always has 20w-50 in it, since it's ahhh, well used.

BTW-all automotive oils are thicker when cold and thinner when hot. There is no magic there.

In the end, though, comparison data is lacking, to show that synthetic oils allow a motor to last longer than conventional oils. OTR trucks go 800,000 to 1,000,000 miles between rebuilds and most of them get run on Rotella and Delo conventional oils. My own *theory* is that having a change interval and sticking to it like religion, is more important than whether you run synthetic or conventional lube oils.