the pamphlet i read in advanced auto stating "once you make the switch to synthetic oil, you shouldn't go back to conventional" has been dwelling on me for a while. i've mentioned it on here before i'm sure but i've never really heard any hard facts on the matter. google search yields countless forum threads with countless answers saying "yeah i've heard that, but i don't know if it's true".

so... is it true? the pamphlet in advanced auto no doubt was funded by someone making money off of synthetic oil, so i tend to think that the draw back to the switch back to conventional would be slim to none.

and before anyone asks "why would you want to?", here's the answer. after i had my heads rebuilt i reckoned that it was safe to use some oil more fit for a newer engine (yeah, false logic, as the oil is doing much more for my older block than it is for these heads), and started using mobil 1. many thousands of miles down the road summer comes and i start seeing a drop in oil pressure, freak out a bit, and now i'm using castrol 10w-40 high mileage and the oil pressure looks great.

 

It's bullshit. I have switched from synthetic to conventional and vice versa many times on all of my race cars without a single issue. conventional oil is first used in break in to help accelerate the wear in process and to clean out the oil passages and all of the assembly lube. (thus why you only use it for 1k miles) a General rule of thumb is, that the hotter the oil is, the lower the pressure will be. But you really have to ask yourself if you trust the stock sender.

 

I'm the same as Hoov, I've had no problems going between synthetic and conventional. I use Valvoline VR1 for hard use since it has a lot of zddp (necessary on these older style engines), and use Mobil 1 synthetic for normal driving on the street. I've put about 80K on my motor since I bought my Z, and no problems with leaks or anything out of the ordinary doing this.

I think it's just marketing hype. Kinda makes me wonder why there are synthetic blends being sold if it's so bad haha.

 

I do believe it does effect seals in some way. but i know this for sure, synthetic can make unknown leaks show up, and flows MUCH smoother, aka acts less viscous than conventional which would explain your pressure symptoms and also why not to be use on break in. you need wear for all the new rings and seals to seat properly. tho if you were to switch i doubt your engine will explode or anything on you, but i wouldn't be surprised if some seals weren't to happy with you. but like most people idk for sure since i have never done it, i doubt it is just marketing hype, but i also doubt its the end of the world if you do it.

 

Sounds like a job for Myth Busters...

 

yeah that's what i figured.

speaking of break in though, how do new cars come? my mom just got a rouge and the first oil change is at 7500, no special instructions.

 

i use 5 w 30 mobil ! sysn... Umm no problem so far my gurls 2009 honda odyessey uses 5 w 20 royal purple ... the engine is super quiet.

 

I have a rebuilt engine. Ran 10w30 conventional for about 6000 miles. Switched to 10w30 mobil 1 and all sorts of things got weird. Stared leaking oil from strange places (including my turbos). Also started hearing some valve tapping during warmup. Didnt put it all together until about a week later when the weather started getting warmer and it was getting worse. I switched to 20w50 mobil 1 and everything got better.

Had to replace a turbo due to blown seals which may or may not have been related

I really did contemplate switching back to conventional so if anyone can find an answer on this itd be nice

 

20w-50 doesn't really have properties that are required for the tolerances that this engine has. why not 10w-40 or something? i've gone back to conventional with no problems, and nobody on here or ANYWHERE else that i've found has been able to say that it was a real problem.

 

20w50 was recommended by the guy who rebuilt the engine. Only with synthetic though. Im sure I could take it down if it were conventional.

So does anyone actually PREFER synthetic over conventional? Because I dont mind paying for it but if this engine is designed better to suit conventional Id like to make only one more switch and stick with the same oil for good.

 

yes, synthetic is MUCH better for preventing engine wear, the thing is, the molecules that make up synthetic are much much smaller,, so those leaks that showed up, were already existing leaks that were being masked by conventional oil. synthetic oil almost acts like a detergent, it will just sneak through any gunk build up and cracks and expose leaks left and right if the motor has any.

 

because your engine builder is soooo much smarter than nissan engineers. engine builders often get put on a pedestal, but the truth is, anyone with the right info and tools can rebuild an engine. it doesn't mean they actually know anything about it.

 

Wow no need to get upset lol. Read my post again and you will see I was simply stating a fact I switched oils and had these problems so I called the guy who built the engine and asked him what was up and he said try thicker oil.

So much sarcasm on this site. You cant even post without people thinking you're being sarcastic.

 

i wasn't getting upset. i also was stating a fact.

it doesn't matter what problems your engine is having. 20-50 is thick for the VG30DE. if you do some research you'll find that oils too heavy will not maintain a coating on the entire surface of your bearings. it's too heavy to flow through the gap at the speed that the engine is turning. this is all as i remember the article that i read. i'll find it again if you can't.

i have heard testimonies of people successfully using 20-50 in the vg, but i was under the impression that they were built with greater tolerances with performance in mind.

 

I just changed my oil and use now castrol 10w-40 ..actually the mechanic said that i should use 5w-40 because its a sports car.. i know i read it somewhere that VG30DETT will run great with 10w-40.. am i right ??

 

yeah, you read that right under the hood. 10w-30 for the winter, 10w-40 for the summer. factory recommendations.

apparently, 5w-30 or 40 is ok now too, and would have been what was recommended from the factory, if it were around back then.

 

Actually i read it on the internet somewhere, not under the hood...
So i should be fine with 10w-40.. do you recommend 5w-40 or the 10w-40 is enough ?

 

Agreed.

I switched to synthetic and any I started to leak oil. I switched back to regular. I think i went regular, synthetic blend, synthetic, and then reverse when i went back. The leaks went "away".

I dont think theres an issues. I heard these two dudes on the radio in like north new york, they have this car repair talk show. Its two old duded who have been mechanics for years, they said theyve done it hundreds of times with no issues.

Everyones trying to make that extra buck.

 

well, it is under the hood too. if it's warm where you live, keep the bigger number 40. if it's hot, make it 50. whether the smaller number is 5, 10, or 20... that's up to you. do your research to figure it out. i myself am running 10 because it's hard to find 5. but, i am strongly contemplating going to ams-oil 5w-40

 

i run 10w-40 in my TT.. My car only really gets driven in the summer. Mobile1.