motor oil question

[peanuthead724]

i have an 09 altima 2.5s, should i use reg or syn oil

[Mr.Coupe]

The decision is yours. I personally have used synthetic on all my cars. Most people will say that with Syn the motor will last longer and perform better. I say go syn FTMFW .

Ricky C.

[SHIFT_COUPE]

Synthetic. Less frequent only changes also.

[wade001]

if the car is new so let it break in for about 15k before switching to synthetic. synthetic doesn't let your seals or piston rings seat. but synthetic is much better i noticed a substantial difference on my last car.

[JSPADES]

Actually, I googled for Q&A synthetic motor oil, and everything I have read on the web says that you can wait as little as 1500 miles before switching over to all-synthetic motor oil.

I will add that most sources say the window for switching over is rather broad, so even an auto with as much as 75,000 miles could still switch over to synthetic. There seems to be a prevailing opinion that the longer you wait, the more you should consider switching to a semi-synthetic oil first. But even that is open to debate.

-b-

[qdemn7]

Newbie here, I just bought a 2008 Altima sedan (45k miles) with 100,000 bumper to bumper service policy. When I asked my salesman about Mobil 1 specifically, he said it might cause problems with rings, seals and other engine parts to prematurely break down.

I have heard this before from other non-Nissan people, concerning other car brands.

Can someone please comment on this?

[el_blacky06]

synthetic oil is alwayz the best way to go. i started using purple oil synthetic at about 22,000 after the dumb dealer blew up my engine. since then itz been good so far no problems once oever

[JSPADES]

Newbie here, I just bought a 2008 Altima sedan (45k miles) with 100,000 bumper to bumper service policy. When I asked my salesman about Mobil 1 specifically, he said it might cause problems with rings, seals and other engine parts to prematurely break down.

I have heard this before from other non-Nissan people, concerning other car brands.

Can someone please comment on this?

qdemn7:

It doesn't sound like your salesman knows what he's talking about. The real issue is that cars with a lengthy history of continuous conventional oil use (a/k/a, dinosaur oil) is that conventional oil will "bake" as it breaks down, to form a sludge around engine (or oil pan) seals and thereby potentially conceal a leak that would otherwise lose oil continually while the engine is running (and sometimes even when the vehicle is at rest!). This, if I understand correctly, is a side-effect of conventional oil breakdown due to overheating at or near the site of the engine seal. As long as the conventional oil is replaced with similar conventional oil, the sludge remains intact and can prevent oil loss, and a leak from being discovered.

When you switch over a car such as this hypothetical one I've suggested, from conventional oil to synthetic oil, the synthetic oil can actually work to dissolve the baked-on sludge left behind by the conventional oil around engine seals, and a seal leak which was once protected by the broken-down baked-on dinosaur oil sludge can then be exposed, allowing oil to be lost. Synthetic oil has taken a bad rap for this phenomenon, when in fact, it is the fault of the conventional oil for concealing what might otherwise be a potentially catastrophic oil leak.

Every car is different. It's possible that at 45K miles, your car might have no problem with the switch over to synthetic (especially if you were to do an interim switch to a semi-synthetic product). It is also quite possible (depending on the maintenance history of the vehicle) that switching over to synthetic might expose a nasty oil leak that you might not be made aware of for a long time, if ever. I would proceed with caution, and if you decide to risk the conversion, be prepared for the worst.

I have read that 70K - 75K miles or so is the theoretical cutoff for even considering a switch to synthetic oil. If, however, you ever get your engine rebuilt, and you aren't switched over yet, it would be a prime opportunity to do so, as an engine rebuild should include getting the engine oil seals replaced.

Additionally, I have heard (don't know if it's true or not) that one shouldn't switch from conventional oil to synthetic oil, and then back to conventional oil. Makes sense to me, though.

-b-

[qdemn7]

great post basilikon, thanks for the information.

[TomNJ]

I've spent my entire 38 year career in synthetic lubricants - aviation, industrial, and automotive. You can break-in a new engine with modern synthetics, in fact, many engines are factory filled with synthetics. That said, I would run your factory fill for 3,000 miles and then change - why waste the oil.

You can also change to or from synthetics anytime you like, and as often as you like, so long as you have maintained your engine well. The issue of some synthetics cleaning out accumulated deposits and exposing leaks is rare and usually only with poorly maintained engines. If you have consistently used SL or SM quality oils, conventional or synthetic, with change intervals of under 5,000 miles, your engine should be relatively clean.

Synthetic oils today are quite a bit different than in the past. The original synthetics were based entirely on diesters which are excellent cleaners, and many of the persistent misconceptions about synthetics date from that period. Modern synthetics are based mostly on synthetic hydrocarbons (Group III and/or IV) and are better balanced for seals and cleanliness. The additive systems have improved greatly as well for both conventionals and synthetics.

Performance with synthetics is clearly superior, but the question is do you need the advantages and are they worth the price. If you want to do extended drain intervals, say over 6,000 miles, or you drive hard or see temperature extremes, then synthetics may make sense. One big advantage is fewer oil changes (I do 10,000 OCIs on Mobil 1 EP or once per year). If you plan on sticking with 3-5,000 drain intervals with normal driving conditions, any SM certified conventional oil will serve you well.

For some more information, see my paper at:

http://www.bobistheoilguy.com/...52107

TomNJ

[Zerep]

our cars use motor oil