synthetic vs conventional

[I'll sho u]

just wondering if anyone has noticed an increase in oil consumption when switching from cheap conventional 10-30 oil to synthetic 5-30. I am going to switch back,but to castrol 10-30 high milage. My oil burning at least doubled when going to synthetic. The engine in the car is extreamley low milage(about 55k) but had sat for like 6 yrs in my friends baby barn and now uses 1 quart per 600 miles. Think that the high milage stuff will help?

 

[wood_e]

In a car that has over 20,000 - 40,000 miles i wouldn't use synthetic unless specified by the manufacturer. Synthetic basically finds every little problem with your engine seals and likes to leak out of them.

 

[SHO_Diehard]

just wondering if anyone has noticed an increase in oil consumption when switching from cheap conventional 10-30 oil to synthetic 5-30.?

For a fair comparison against conventional 10-30, you should run synthetic 10-30.

I am going to switch back,but to castrol 10-30 high mileage. My oil burning at least doubled when going to synthetic. The engine in the car is extremely low mileage(about 55k) but had sat for like 6 yrs in my friends baby barn and now uses 1 quart per 600 miles. Think that the high mileage stuff will help?

Is there oil leaking from the engine, or are you burning that much? If it's burning it, I would think you'd see smoke from the exhaust. If it's leaking that much, change the seals.

I started using synthetic in my '89 at 20k, it's at 195k now.

 

[I'll sho u]

smoking from the tail pipes,think it is the valve seals.

 

[SHO_Diehard]

smoking from the tail pipes,think it is the valve seals.

Smoking on acceleration, or when you let off the gas?

 

[SHOv6]

I just switched my SHO over from dino-oil to Mobil 1 synthetic at 114Kmiles, and I have no leakes, and the car runs beautifully!

 

[FAST4DR]

Mine(84,000 miles) is starting to show a puff of blue smoke during hard acceleration, during high rpm lift throttle and when I re-apply the throttle it will throw a puff of blue smoke and after sitting a long time when I start it up it will throw out a puff of smoke. Other than those three conditions it is fine. I'm pretty sure it is the valve stem seals. The high rpm puff of smoke is probably the zero vacuum and then going to full vacuum when the throttle is closed forcing oil down the valve stem seals and then back on the gas and it burns the oil.

So in the end yes it uses a little oil. I may add a half quart between oil changes, which I usually let go for about 3-5000 miles. I use Mobil 1 5w-30.

I have actually read that you will use less synthetic oil than conventional oil because the molecular structure of synthetic is more consistant than conventional oil. I dunno. Just what I read somewhere.

Will

 

[Redline]

I was told by a mechanic friend of mine (a smart one!) that synthetic will leak easier that conventional. He also said that it is better to stick with conventional oil if that is what your engine has always run. Consequently, I have stuck with conventional oil.

 

[FAST4DR]

I was told by a mechanic friend of mine (a smart one!) that synthetic will leak easier that conventional. He also said that it is better to stick with conventional oil if that is what your engine has always run. Consequently, I have stuck with conventional oil.

No offense, but blaaaaaaah. Does he have a degree in Chemical engineering? None of really know unless we are chemical engineers that work and study this stuff.

And, "If that is what your engine has always run"? These things are not alive. It just a bunch of metal parts.

Not trying to be mean, it's just that there is so much unknown information that 99.9% is all conjecture.

Will

 

[SHO#7]

I see both my 96 and my 93 use a little more oil since I have switched them to Synthetic 10W-30. My 93 has 130k and my 96 has 128k.

And from what I heard, the max life oils are partial synthetic.

Mike

 

[Dan H]

I'm not a chemical engineer, but I am an aerospace engineer

and I won't run anything but synthetic. It is far superior to conventional in almost every way.

 

[SHOtimer]

It is far superior to conventional in almost every way.

How so?

Doug

 

[Dan H]

Synthetic oils bond to surfaces better and have a lower friction coefficient, so they are a better lubricant. Also, and probably more importantly, synthetic oils molecular structure doesn't break down due to age and thermal stress as conventional oils do. The main reason conventional oils must be changed every 3 months regardless of milage or every 3000 miles regardless of age, is due to molecular breakdown. Conventional oil will breakdown very quickly if overheated, synthetic will maintain lubrication at much higher temperatures. This means that synthetic is much more forgiving of infrequent oil changes, hot temperatures, and low oil conditions. I have seen more than one engine destroyed that might have been saved if synthetic oil had been used. Gas turbine engines require synthetic oil due to its superior properties in harsh conditions (high thermal stress, high rpm). This is also why many turbo charged engines should always use synthetic.

If you change your oil religiously every 3000, or 3 months (which ever is sooner). Never heat your engine past normal, and check your oil level every day or two, conventional is fine; it just doesn't have the extra margin that synthetic does.

 

[SHO_Diehard]

I'm not a chemical engineer, but I am an aerospace engineer

and I won't run anything but synthetic. It is far superior to conventional in almost every way.

Hey, I’m a chemical engineer :wave: In fact, I provided tech support to a Group I base stock plant a few years ago. I’ve got a ton of experience in general refining type hydrocracking (hydrocracking is used for Group II base stocks). I agree with the statements in your other post.

I did some internet research on the topic last night, I was surprised at the revised use of the word "synthetic". (old news to some people, I've been too busy repairing our three SHOs to stay current on that topic.) Group III is apparently a highly processed base stock, but the starting point is still crude (not 100% on that). Group III is actually classified as a synthetic, there is some interesting reading about that on the Amsoil web site.

 

[olympic]

This chart shows that Xw30 oils actually fall into a range of viscosities, ranging from 9.5cst to 12.49cst(scroll down for more clarification on this) High mileage oils tend to be at formulated the upper end of the range(thicker), synthetics like Mobil 1 tend to be formulated at the lower end of the range(thinner). This could explain alot of the oil consumption issues that people have when switching to synthetic. Surely there's more invloved than viscosity but it'd probably a big part of it.

Having sat for 6 years, the valve seals are probably dried out and leaking. A thicker oil may help but it's a bandaid at best. It's also possible that one of the ring packs have gotten stuck and arn't sealing properly. A full treatment of auto-rx would fix that right up.

 

[JTSHO]

well im no engineer, buttt, when i switched from conventional to castrol high mileage 10-30 in my 92 mtx at 90,000 miles and my 93 atx at 80,000 the oil consumption definitely was cut in about half. what ive heard in the past is that the high mileage contains additives to swell seals and lubricate better. just my .02 :corn: