Switching from conventional to synthetic oil?

CobraStang95 · Jul 22, 2004

Just wondering if it would be OK to switch my 90 GT that has 129,000 miles from conventional to synthetic. I've heard three different things; that your not supposed to do it, that you have to gradually do it with semi synthetics, and that it doesn't matter at all. I want to put in Valvoline Max Life Synthetic, but will it be alright? thanks in advance...

Ray III · Jul 22, 2004

synthetic is high detergent and will strip any gunk that might be plugging an otherwise leaky seal. If your engine is especially filthy (Quaker State convert) you may plug the filter pretty fast as it goes through engine deposits. If you're prepared to replace any seals that might start leaking in the near future go for it.

MaxLife is supposed to slow leaks anyways, so it might be a wash.

timewarped1972 · Jul 22, 2004

the battle always rages on this subject so i took it upon myself to take the easy way out..............i use a dura blend or the half n half mixes ( also cheaper ) and change the oil every 1500 miles or when it gets dark just because i'm a pin head...........

bsedwebt70-5.0 · Jul 22, 2004

Just do it - no problems - I have done this many times without a hitch - Use the CHEAPEST FULL SYNTHETIC you can find in the lightest weight that does not burn too fast in your engine and go for it - I like to use SYNTECH - WalMart house brand at 2.80/quart - All full sythetics are the same... I also like to add 1/2 quart of DuraLube for each oil change and go 6k for changes.

_jb_ · Jul 22, 2004

bsedwebt70-5.0 said:
Just do it - no problems - I have done this many times without a hitch - Use the CHEAPEST FULL SYNTHETIC you can find in the lightest weight that does not burn too fast in your engine and go for it - I like to use SYNTECH - WalMart house brand at 2.80/quart - All full sythetics are the same... I also like to add 1/2 quart of DuraLube for each oil change and go 6k for changes.

lol Walmart brand. I think i will stick with Moble 1 or Amsoil. $30 a case of Moble 1 is worth it IMO.

TrophyHead · Jul 22, 2004

I use the Syntech blend by Castrol.(I think its like half and half) I started leaking oil after I put Mobil 1 in. The Castrol seems to run better but I'm using 20W-40. Oh my car has 120,000 on it.

ironmedic · Jul 22, 2004

i am messing with 5w30 royal purple

89MustangGX · Jul 22, 2004

bsedwebt70-5.0 said:
Just do it - no problems - I have done this many times without a hitch - Use the CHEAPEST FULL SYNTHETIC you can find in the lightest weight that does not burn too fast in your engine and go for it - I like to use SYNTECH - WalMart house brand at 2.80/quart - All full sythetics are the same... I also like to add 1/2 quart of DuraLube for each oil change and go 6k for changes.

All the same ... I think not. But you're right about Walmart, they do have some pretty good prices on oil. personally, I like their 5 quart jugs of Mobil-1 -- usually around $19.

Daggar · Jul 22, 2004

I have waaaaaay over 120,000 miles on my shortblock and it shows no signs of wear whatsoever. I've been using Valvoline Full Synthetic 10w-30 in the winter and either 10w-40 or 20w-50 in the summertime. I do understand what they're saying when cautioning about switching over to synthetic after such a long time (you may find leaks that you never saw before). However, there's no point in trying to "ween" your engine from the hard stuff. If you do spot leaks then I'd think that it would be better to replace a warn seal now than a broken or torn one later. The longer you run that 'other' stuff the more wear you're putting on your engine. If by switching to full synthetic you discover problems then those are problems that need to be addressed; not masked by a poor quality motor oil. That said... I doubt that you will encounter and problems with the switch.

Michael Yount · Jul 22, 2004

The car's made it this far in reasonably good shape on regular dino oil - why do you want to switch? As mentioned above, a significant number of people switching high mileage vehicles from dino oil to synthetic experience leaks. As for wear - continue to keep your oil/filter clean, and you needn't worry about excess wear even with dino oil. Irv Gordon has over 2 million miles on his 67 Volvo - 1.4 million miles on the same head/valve job, all 2 million miles on the stock bottom end/rings - all on regular dino oil and Volvo oil filters changed at the factory required interval. If he can make 2 million miles on regular dino oil, you can probably get another 130,000 out of yours.

88stangmangt · Jul 22, 2004

timewarped1972 said:
the battle always rages on this subject so i took it upon myself to take the easy way out..............i use a dura blend or the half n half mixes ( also cheaper ) and change the oil every 1500 miles or when it gets dark just because i'm a pin head...........

wooooooooohhh bad idea on the color decision............. if i was to change fluid in every differential that i worked on because of color i would be a busy man...... i personally use amsoil..................and i love it tends to be expensive but will save you in the end. but if any leaks (small or not) are present synthetic will make them worse.

timewarped1972 · Jul 22, 2004

well, imo, sometimes milage intervals are not reliable. it's dusty where i live, and also have noticed a properly maintained frequently oil changed engine will not dirty the oil fast. the oil in some engines gets dark fast because there's already sludge and crap in it. when the oil starts getting real dark it's because it isn't clean and depending on the driving you do it can start to cake up on stuff.........better safe than sorry and it's cheap insurance.....differentials are one thing, engines another..but like i said, i have always been fanatical about air filters and clean oil.........i can't think of a better obsessive compulsive binge!.....lol

HISSIN50 · Jul 22, 2004

if switching, as touched upon, i would do a short OCI, since there might be some sludge that has been broken loose. also, as said, not all syns are the same. some mentioned in this thread are group III's (highly refined hydrocracked base). others mentioned use PAO (and some PAE's) base stock.

The Shape · Jul 22, 2004

I switched recently to mobile-1 15w-50. My rear main leak may be just a bit worse, but not that bad. I only switched though because I wanted a heavier weight oil that I could run year round for pressure reasons. I didn't feel good about running dino 20W-50 in the winter, but the mobile-1 15W-50 synthetic is supposed to flow at a lower temp. than regular 10W-30 dino oil so I went synthetic. I also did as HISSIN50 suggested I changed to the synthectic ran it for about a week and changed the oil again just to make sure I got any sludge that the synthetic oil broke loose out of my engine.

Michael Yount · Jul 22, 2004

Just to clarify - there's not a one size fits all on change intervals. Depending on temps, how hard the motor is used, climate, etc. - everyone has to make their own decisions. However, it's also fact that color of oil is not an accurate indicator of the oil's ability to do it's job. Over the road truckers and big fixed engines for industrial applications (among others) don't change on regular time or mileage intervals; they pull oil samples and have them analyzed -- the results tell them when to change. My brother approaches changes on his F350 PowerStroke diesel the same way. It's loaded with a bunch of Gale Banks performance stuff - makes about 350HP/600 lb-ft of torque. He routinely goes between 17,000 and 25,000 miles on Amsoil synthetic between changes based on analysis. That oil is quite dark (it's a diesel after all) after just 4 or 5 thousand miles - and as you can see, it's still working quite well long after that. And that's one advantage of synthetic - you can go longer without breaking the oil down. How much longer depends on the application. But non-syn oils are perfectly capable of protecting - just not for as long especially under extreme conditions.

timewarped1972 · Jul 22, 2004

i'd agree, it just seems like when ever i pulled a valve cover on an engine that had cleaner looking oil that had been changed often everything looked clean as opposed to engines with dark or black oil having sludge everywhere. between the heat and the dust in az, i'll continue being a pin head and keepin it clean......

Michael Yount · Jul 22, 2004

"i'll continue being a pin head and keepin it clean......"

Nobody can call that a bad idea.

timewarped1972 · Jul 23, 2004

lol..........as long as i dont cross-thread my drain plugs i'll be ok i think. besides, i have to change it frequently as it's become my trade mark and a running joke among my family and friends.....
really its amazing, i did a search and there is so much controversy, info, brands, blends, additives, and so on its mind bending, especially when people just are just trying to buy a good oil for their car......look at all the confusion and controversy all of the oil additives over the years have caused.....all the late nite infomercials........motor up, slick 50, pro long duralube, and the list goes on and on, thats why i said long ago forget it and change it frequently and forget about it.......i wonder if all this has confused the individual who started this thread yet????

white_90_GT · Jul 23, 2004

I've been using Castrol Sytec for a long time now in all of my cars and never had any problems. But my buddy swapped to Mobil 1 in his truck at 450,000 over 300,000 where on engine rebuild ( 460 ). Not a single problem there either.

Just anothe one to think about.

--Casey

HISSIN50 · Jul 23, 2004

Warped, i am quite a bit in agreement with you, as well. we know what the desert heat is like (Tucson, for me. Michael used to race in Texas, IIRC). as i recall, dino oil, if kept at 250* or more, for much of a period, breaks down much faster. our 5.0's can see 250 without breaking much of a sweat (though i might). as long as you can afford it, do the changes as you do. but for not much $$, but can get a UOA done and know how the oil is doing.
in general, guys running cheap dino oil often go 5K (based on lifespan/#'s from UOA's). we tend to be stuck on the 3month/3K mile stuff, though the oil can go longer. and i am as bad as anyone - i grew up with dino oil and the 3/3k stuff myself. ive changed oil that was 6 months old, with 20 miles on it (worries about water and sulfur dancing together and creating acid).

Michael puts it best - in essence, to each his own. no one is really more correct than anyone else.
i am watching the oil cooler thread - hoping to see some responses about what is the best way to go.
:OT: Michael, your brother went from the FJord to the big diesel..? hmmm, he is quite the connoisseur of fine, albeit vastly different, vehicles.

Switching from conventional to synthetic oil?

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