Settle this for me once and for all:

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Jim Prower

Jim Prower

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Will Synthetic Oil have a greater tendency to burn off and/or have low oil pressure in a 140,000 mile, 15+ year-old engine? I bought some Royal Purple, but Dad warns me against putting it in there. Is he right, or just old?
 
Now I'm no expert in this and just going on my personal experience. I have a 14 year old 2.6 Audi A4 with 160,000+ mile on it. Bought it as a cheap runaround for DIY etc..Been servicing it myself with fully synthetic oil, done three oil changes in it so far and hasn't used a drop in between. The oil pressure light goes off so fast when I start the car in the mornings that I hardly have time to see it, so I guess it still has pretty good oil pressure! Like I said, not a pro or anything but on my experience I havn't had any issues yet.
 
Synthtic will be a little thinner, so in my little world it would make sense that, let's say your car reccomends 10w-30 conventional, go for 10w-40 symthetic, to make up the difference in the viscosity.

Please correct me if I'm wrong, this is purely a common sense speculation.
 
I've been using fully synth in a 20 year old/100,000 mile engine for a few weeks now and oil pressure is identical to how it used to be. What it'll be like in another 10k I don't know, but so far it seems the same as it was on mineral oil.
 
Jim Prower
Will Synthetic Oil have a greater tendency to burn off and/or have low oil pressure in a 140,000 mile, 15+ year-old engine? I bought some Royal Purple, but Dad warns me against putting it in there. Is he right, or just old?
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If your engine hasn't been maintained and is full of sludge, then yeah, Synthetic oil might reduce your oil pressure by clearing out the buildup and reducing restriction. If your engine is clean, then no, shouldn't make a different provided the viscosity is the same.

He's just old.


Worst case scenario you've got to put regular oil back in.
 
I use full-synthetic on my 96 Miata with 78k miles...as long as the engine is cared for and there are no problems already you should be fine. It cleans it out much like a body flush. I love it.
 
I'm not an expert, either, but I know where you can find people who are. (Warning. Those guys are serious about oil):

http://www.bobistheoilguy.com
And a link to an article on that site, which includes a lot of info on synthetics. I scanned it again, but I didn't see anything about burn-off, but a great deal on thickness at various temperatures of both synthetic and mineral.
Motor Oil 101
 
I have heard this dozens if not hundreds of times on the Internet - people swear synthetic oil is bad for older engines. They never have a concrete reason why, though.

I run Mobil1 in everything I have, which ranges from 35,000 miles to 270,000 miles, and I have seen no greater tendency to burn or leak, no lower oil pressures, no nothing. It's BETTER OIL. How can it be bad for the engine if it is the right viscosity/weight?
 
My Civic Si ran perfectly well on Mobil 1, and after 153,000 miles the valvetrain is spotless. Not a spec of buildup in there anywhere, and everything is still nice and shiny. Good, clean oil is good, clean oil.
 
Well, I do believe that settles it...other than one thing....

Anyone have experience with the Royal Purple brand?
 
I use 10w-30 Castrol Edge full-synth. Every 3k miles. My engine is pristine. I only drive an average of 15-20mi a day except weekends usually 50-100.
 
You change synthetic oil every 3,000 miles? Why? Unless you drive insanely hard there is no reason too.
 
Joey D
You change synthetic oil every 3,000 miles? Why? Unless you drive insanely hard there is no reason too.
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Even then there isn't much reason unless the car has blowby issues or something... In which case you may as well just use dino sludge as it's screwed anyway.
 
Jim Prower
Anyone have experience with the Royal Purple brand?
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Royal Purple isn't the most practical option for street use. It's the same type of synthetic as Mobil 1, Redline, and other performance oils, that is, "real" synthetics, but unlike Mobil 1, Royal Purple and Redline are designed for performance applications, not long-lived street use. They lack some detergents that are found in street oils in order to keep your engine clean, but they trade those for extra lubricity. Royal Purple is also noticeably more expensive than Mobil 1. Mobil 1 is pretty much the best street option of them all.

fitftw
I use 10w-30 Castrol Edge full-synth. Every 3k miles. My engine is pristine. I only drive an average of 15-20mi a day except weekends usually 50-100.
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Castrol Edge isn't considered fully synthetic anywhere in the world except in the United States. In fact, I can't find any reference to any Castrol oils being "real" API 4 or API 5 base stocks, other than some bearing greases and this stuff called Castrol Elixion, both of which are polyalphaolefin-based synthetics. Elixion is a special "off-road" oil for heavy trucks and whatnot, but all their street "synthetics" are API 3 base stocks. On the other hand, information explaining that all Mobil 1 synthetics are based on polyalphaolefin or synthetic esters, being API 4 and API 5 base stocks respectively, is readily available on their website.

Not to sound stuck up, but when you have a rotary it's good to know which synthetics are the real deal if you want your engine to last more than a week. Grade 3 synthetics will foul a rotary quickly because they don't burn clean, whereas API 4 and API 5 oils will work because they burn properly, just like conventional oil. Mobil 1, Royal Purple, Redline, and other high-end racing synthetics can be used in a rotary with no ill effects. But it just so happens that they're at least twice as expensive as conventional, so of course I do use conventional.

And no, you don't have to change synthetics, even crappy ones, every 3,000 miles. They're designed to break down much more slowly than conventional. But despite that, clean oil is always better than dirty oil so if a person can afford to change it as often as possible they'll be better off.
 
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Jim Prower
hm...Wonder if I kept my reciept, then.
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Why? Royal Purple is still good, I would just switch to Mobil 1 on the next one just to save some money.

In fact, I ran Mobil 1 for 3 years in my Civic and then switched to Royal Purple on my last oil change before I wrecked it and the engine felt noticeably smoother.
 
Hey, if he's got the receipt he might as well save his $10 this time, too.
 
For older cars that never had synthetic before; use a syn/dyno blend (semi-synthetic)

If you have any leaks, even if they're small, they usually get worse when you make the switch to a full syn. If you switch back to regular oil, the leaks will still be there. With Royal Purple; they use moly and other bits that actually polish surfaces. While this may be good for a very low mileage car - I wouldn't recommend this for one that's been around the block a few times as any tolerances are probably even greater.

Another thing to keep in mind is that all new oils have to meet some asinine enviro-mental standard. Older oils used zinc & phosphorus as a wear inhibitor, however the greenies think this destroys catalytic converters. The compound is often referred to as 'ZDDP' - newer oils do not have this...unless...they're labeled as 'high mileage'.

And there's what you need - a high mileage semi syn. I'd recommend Valvoline as you can find that stuff in any parts store. Pennzoil & Castrol are terrible oils. Where a good conventional oil is still doing its job 6,000mi later - the additives in Castrol or Pennzoil break down in less than 1/2 that time. You can lift the valve covers on any car and tell if it used Castrol, Pennzoil, or something else.

Typically, you should change a conventional/semi-syn oil around 6-7,000mi. Any less time and it's actually worse for your car. If the oil is dark/black - that's not a bad thing. That means the filth in the engine is being emulsified by the oil, like it's supposed to, and not deposited somewhere else.

Just in case you don't know what oil I'm recommending;

41ACK5GKY9L._SL500_AA300_.jpg


Red bottle = blend or semi-synthetic
Silver bottle = full syn
 
I think we should be clear on which RP product we're talking about. I've had no complaints about RP in the time I've been using it.

The idea that synth is bad for old engines dates back to when mineral oils would help seal gaskets and synthetics would wash this away and start leaks. But you'd have to be driving an awfully old (say... 30-40 years old) clunker for this to be a problem.
 
I was told the Pontiac would die from unleaded gasoline, too, and it's got about 80,000 miles on it that prove otherwise.

I've heard people with old engines who like to use synthetics for diesels (like Rotella) because these typically have more zinc in them for wear since diesels go for so long, and also they have more getergents in them because diesels are dirtier inside.
 
Jim Prower
Well, I do believe that settles it...other than one thing....

Anyone have experience with the Royal Purple brand?
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:lol: I love this stuff. I have had pretty moderate use with Royal Purple as a brand. And I was using Valvoline max life before it. Believe it or not, I use it in my Buick Electra as well as my RX-7. In fact, when I had Midas change my oil (because it was free) they were almost reluctant to change it because it still looked clean, even after about 9 months. I really love it.:)
 
Well, I'll throw what i've bought in it, check my oil when I fill up (as always,) and probably go Mobil 1 next time. Thanks for the help guys!
 

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