Guys,
I just made a road rip from Houston to Florida and did an oil change in the mobil gas station there. The mechanic told me that once my vehicle is on syntetic oil, I should not change it back to normal oil as it would mess up my engine real bad. This is the first time I have ever heard of such logic. What do you guys think?

 

BS!

Just don't extend the drail interval with regular oil. The synthetic and regular oil are compatible.

If what he said is true, how come they sell vavoline semisynthetic blend (half synthetic and half regular).

Again BS

 

hmm, i dont think it would do anything to change back to normal oil... dont some cars come with synthetic and some of those people put in normal oil?

 

Ummmm...I'm no expert, but EVERYONE I've talked to (friends, mechanics, etc...) has told me that once you go sythetic you shouldn't go back. I'm going sythetic next time I get a change and I'm staying sythetic after that.

 

My brother is a moderator on the F-body forums and he is good friends with the "Oilman". The Oilman is a Chemical Engineer for Lubrication Engineers testing labatory and they have done extensive testing on all types of oils for both the military and civilian world.

The problem with changing oils is primarily with older engines (pre-90's) on dino oil. If you put synthetic in them, they have enough age that the seals may not be in perfect shape and they may have the older style composition gaskets in the engine. The synthetics aren't exactly a "creeping" oil, but they have a smaller molecular chain that makes them really "flow" and they don't make the seals/gaskets swell like the dino oils do. The result is usually leaks that get progressively worse and is why there is a lot of people saying not to switch back and forth. In your case, you have a new enough engine that it won't be a problem since it has RTV for most of the gaskets and the seals are made out of a much better oil resitant material nowdays.

If you are worried about the incompatibilities of mixing the oil, there are a few partial synthetic oils on the market such as Valvoline Durablend. They use a combination of dino and synthetic oils, so mixing them is not an issue.

I don't want to get in to the battle over dino v/s synthetic, there are pros/cons to both and you should judge for yourself. In my own case, I have some past experience building H/Perf. V-8's and have used both dino and synthetic in them. I found that if I used a low wear # dino with a high oxidation number, used a quality filter (not Fram!) and kept it changed at 3k intervals, the teardowns were always as clean as the synthetic motors and nearly as tight when originally put together.

The following is something you might find interesting. It was some correspondance from my brother(Curt)to the Oilman(Kevin). Since it's an email, start at the bottom and read up. I have always used Valvoline All Climate oil and my Bro uses Lubrication Engineers in his '96 WS-6 Firebird. He's pushing 400+HP at the rear wheels with the mods he's made and is doing a complete teardown of the motor this winter(he's installing a nitrous piston/crank/rod kit and internally balancing the motor). He's mic'd all the clearances and there is amazingly little wear with over 120K on the motor.

--------------
Curt,
The reason that I say they are a waste of time is that we are in a different market than they are. Most of our business is in 55 gal drums and up to 8,000 gal tanks. We are not set up to sell small quantities or be in the retail market like those other companies are. Conversely they are not into the industrial or big truck market like we are. So it would not be very beneficial to LE to test against those companies.

Test oil -- P/F -- Wear# -- TFOUT (oxidation)

Castrol GTX -- Fail -- NA -- 121
Havoline Formula 3 -- Pass -- 14 -- 193
Honda -- Pass -- 14 -- 323
Mobil -- Pass -- 16 -- 218
Mobil 1 -- Pass -- 12 -- 509
Mopar -- Pass -- 19 -- 237
Motorcraft -- Fail -- 207
GM Goodwrench -- Pass -- 16 -- 221
Pennzoil -- Fail -- 231
Quaker State -- Pass -- 11 -- 157
Total Quartz 5000 -- Pass -- 17 -- 219
Toyota -- Pass -- 14 -- 222
Phillips 66 Tropartic -- Pass -- 17 -- 153
Valvoline All Climate -- Pass -- 17 -- 247
Valvoline Dura Blend -- Fail -- 166
Western Auto -- Fail -- 190
Lubrication Engineers 5w-30 -- Pass -- 6 -- 481

Look for low wear# combined with a high TFOUT# (oxidation) and you will find the best oil.
Kevin
---------------
Kevin,
Can I have the updated list anyway? Why is Amsoil, RedLine and Royal Purple a waste of time? I see quite a few people say they use it, but I know it's snake oil. I was just hoping to have some ammo as to why
Curt
----------------
Curt,
The updated list of the 5w-30 oils does not list Amsoil, Redline or Royal Purple. Those oils are not very much competition so a waste of time to test.
Kevin
----------------
Kevin,
I was wondering if I could get an updated list of all 5w-30 and 10w-30 oils that you have tested. I'd especially like to see some numbers from such oils as Amsoil, RedLine and Royal Purple if available.
Curt

 

My grandmother's third cousin twice removed said you could go to the mobil site and read the faq about Syn/Dino compatibility. It addresses all these questions.

You can rely on other people's opinions, but the manufacturer's publish answers to these questions. I mean, you are *already* on the internet, you could go easily to the horses mouth, so to speak, and address your concerns.

 

Anyone know what the TFOUT (oxidation) numbers mean???? I'm a Mobil 1 user, so I'm concerned as to whether a high number is good or bad... Unless I'm told differently, I'll assume high is good, since the "lubrication engineers" number is also higher than the others. I assume that as being good because I assumed that to be an oil made by the engineers as being a good oil. Also, I take it that the lower the Wear# the better...

Oh, I need to read more closely next time,sorry.

 

here are a lot of myths about motor oil - that's one of them, but it is based loosely on fact. If you are running on synthetic and then change back to dino you lose the benefit of synth. Then if you change back your first load of synth. is really a blend due to the remains of dino in the engine. No big deal, just better to stay synthetic.
Incidentally - 3k oil changes is myth #1 - engines and oils are much better than they were in 1940 or so. Why do you suppose that the Ford focus sold here has recommended 3 - 7.5k oil change interval but the ones sold in Europe are 12k?

wdave

 

it wasnt in the FAQ a few months ago but i emailed Mobile and asked and their response was that if you use synthetic (Mobile 1 specifically) and want to go back to regular, THERE IS NO PROBLEM WITH DOING THAT. althought, the letter said "Mobile 1 is comptaible with all non-synthetic motor oils" but it didnt address the issue that Carl brought up.