Synthetic and Regular oil mix in an LT1:

[92ghost]

A friend at work who owns a 93 40th aniv. edition told me that she had to top off her oil with about 1/4 cup. She then proceeded to tell me she used Penzoil and asked if it was a good brand. I immediately asked if it was a synthetic type as I don't belive Penzoil makes a syn. She said she wasn't shur but did not know what a Synthetic type oil was, so I am assuming it was fossil type oil that she added. I said if it were me I would drain the oil immediately and put in fresh Mobil 1 because of what I have heard -- the two types do not mix well and may cause damage. However; I wasn't sure what could happen if only 1/4 cup of oil was all that was added.

So, is this a recipe for disaster or am I being overly causious? She said she will go 2000 miles before changing the oil again. She takes it to a dealership so I am positive it has Synthetic in it from the last oil change...

 

[Aurora40]

Mobil 1 will mix with conventional oils:

http://www.mobil1.com/USA-English/MotorOil/Synthetics/Synthetic_Oils_FAQs.aspx#FAQs5

 

[Mad-Mic]

all syntecs will mix with conventional oil. it's backwards compatable. i've done it a few times and i change every 7-10k in miles.

 

[G Winter]

Penzoil , eeewwww. I wouldn't put that in my worst enemie's car.But I believe all synthetics will mix with conventional oil. What else would the blends be? She should be ok till the next oil change. She should check with the dealer and make sure they are putting synthetic in it, isn't that what the LTs call for?. Wouldn't hurt for her to keep a qt of the type of oil that is being use on hand. MHO

Glenn

 

[Edmond]

I believe '94 was the first year when synthetic came from the factory.

 

[c4cruiser]

1992 was the first year for the LT1 and all LT1's and LT4's got Mobil-1 synthetic oil as the factory fill. The major reason for using synthetics was that the oil cooler in the earlier L98 motor was deleted for cost and weight savings when th eLT1 was designed. Going to a synthetic allowed a slightly higher oil temp to not be an issue with the new motor and synthetics were able to handle much high oil temps compared to dino oil.

A 1/4 cup (2 ounces??) would not hurt anything as the oils will mix. If she checks the dipstick, she should see a crosshatch pattern on the stick and an oil level anywhere within that pattern is fine. I believe the length of the pattern on the stick is supposed to represent a half-quart.

As far as Pennzoil is concerned, IMHO, it's an excellent oil. I have used it for over 30 years in a wide variety of street and race motors and have never had a oil-related failure. I've never had a motor show signs of sludge or other build-up with Pennzoil.

 

[G Winter]

I worked on many engines over the yrs. Anything with penzoil was a mess inside. I also noticed that with penzoil that if the oil wasn't changed before 3000 miles it would suddenly break down and the engine would start burning it. [ I ran a service station for a number of yrs] Over 40 yrs of driving the only two engines I ever destroyed were running penzoil and it wasn't due to abuse or high milage. The oil failed to do it's job. Try a test. pull dipstick out with penzoil and rub it off with finger and thumb , now rub finger and thumb together , you get down to the finger and get friction very quickly. Then try it with mobil, havoline , or any of the other major brand oils, you almost can't get to the point where you have friction between the finger and thumb. In my opinion that means the oil will also do the same on friction parts in an engine. I have talked to many other mechanics that feel the same way , many will not warrenty a rebuild if you put penzoil in it.

Glenn

 

[92ghost]

Thanks for the replies and the links...

 

[JPS]

Wow, that's bad news for Penzoil, we should ask them for a reply. I change oil every year, because I feel I have to. It is Kroon oil which is Dutch. Is there a comparison between different oils in combination with Corvettes?

 

[vetteboy86]

I am a firm believer in the Castrol Conventional oil. However in sythetics Mobil has to be the best. Why else would it be factory fill???

 

[Edmond]

I hear that Amsoil and Royal Purple are also very good synthetics. In fact, they did a swap of the stock fluids in an SS or Z28 Camaro a few months ago from the factory fill to Royal Purple and picked up something like 8 or 10 horsepower. But I'm sure some of that has to do with having fresh fluids in the vehicle in general.

 

[aboatguy]

I hear that Amsoil and Royal Purple are also very good synthetics. In fact, they did a swap of the stock fluids in an SS or Z28 Camaro a few months ago from the factory fill to Royal Purple and picked up something like 8 or 10 horsepower. But I'm sure some of that has to do with having fresh fluids in the vehicle in general.

Mobile One, is compatable with conventional oils.
It is due to the reduced friction of the synthetic lubes. I put when I put Mobile gear lube in the two diffs on my wife's 5.9 RT she thought there was something wrong with the brakes becuase it would not roll to a stop any more. (before the gear oil change it would coast down to a slow roll afterwards it would idle at 15-20 mph) However, this was on a full time 4WD a regular 2WD car will not benefit as much, however, I use Mobile One gear lube in the rear of my 95 Vette and have no problems and I often beat my Vette like a 2 dollar mule.

 

[Edmond]

and I often beat my Vette like a 2 dollar mule.

:L:L:L I think that's the first time I've heard that expression.