can I mix mult-viscocity oils?

[zliminator]

I had 2 quarts of 10w-30 syntech and went to buy some more, not knowing what I had. I got 4 quarts of 10w-40. Should I take it back for 10w-30? Its for my 350v8z and its pretty much broke in with regular oil.

[fl327]

Sure you can. On my toyota p/u, it will burn a quart every 1000 or so miles if I use 10-30, but I go three qts. 10-30 and one quart 30w, no more and a super quiet running lil truck. On my turbo car I run two quarts of 15w-50 synth with three quarts of 10w-30 synthetic, and have been doing it for years now.

[BrandonsZ]

OIL: The True Story,

 

You can put anything from 10W to 50W or any combo therein in every hole in your car ecxept the automatic transmission or power steering pump. The viscosity oils are better for cold weather and better performance, higher viscosity oils are for hotter weather or better wear protection.

 

If you put straight 10W in a car and drive it in the desert consistently, you might have premature wear. If you use 50W and drive it in the snow consistently, you'll probably have trouble starting it, and might bust your oil pump, or have insufficient lubrication.

 

You can mix them all you want, you can mix synthetic (Syntec) and regular oil (not Mobile 1 check the bottle) Otherwise in about 100 miles the oil will be completely mixed anyway and they'll be pretty much combined to act almost exactly like a hybrid of the two.

 

In fact you can put engine oil in your diffs and tranny too, it's not a big deal as you might think, but they could wear faster. I have used synthetic 10W40 in my manual transmissions (one for over 200k) and never had a single problem with my transmission, and I beat it up believe me.

 

Just keep in mind the colder the weather the lighter the oil and via versa.

 

If you want higher performance use the lightest weight oil you can given the temperature of the climate you live check any good reference book for the ranges. If you want the best protection, use the heaviest weight you can for the climate.

 

Lighter weight wears faster, but reaches further. Heavier weight wears longer but might lose the ability to lubricate int he lowest temperatures or smallest passageways, that's why multi-visc is so nice.

 

If you want to put it in and forget about it, use 10W40 all the time and you are pretty well covered for anything, but keep in mind 10 W oil will seep through gaskets easier and a leaky engine will leak faster with the lighter oil, if you leak, shift to 30W and you'll be ok for anything but snow conditions.

 

Also...

 

Synthetic oil should not be used in new engines because it does not allow the rings to seat properly, synthetic oil should not be used for the break in period or 10,000mi whichever is longer. Otherwise 1 quart of synthetic mixed in 4 quarts of regular will give as much protection as full synthetic, but half the cost. And Synthetic penetrates much further and is "slipperier" than regular oil so you can afford to use a heavier weight like 10W40 and still have good performance.

[Pop N Wood]

I have *heard* you shouldn't mix brands of oil since you can't be sure how the different additives will interact. I have also read that 10W 40 is not a good oil, that 10W30 is all the wider of a ratio you should use. Something about the polymer chains being too long to try and get the 40 part.

 

Both of my Toyotas recommend 5W30, so that is all I run.

[Tim240z]

The LT1 engines say "use ONLY 5W30"......not just recommended, but "ONLY"!!!

[BrandonsZ]

Now that I think about it, my info is probably more for older cars. For newer engines, always follow manufacturer recommendations, but given no recommendation... See above.

[Toysport]

I had 2 quarts of 10w-30 syntech and went to buy some more, not knowing what I had. I got 4 quarts of 10w-40. Should I take it back for 10w-30? Its for my 350v8z and its pretty much broke in with regular oil.

 

I heard that if you mix your oil with different weight's......you can contaminate it.

[BrandonsZ]

Contaminate it with what?

[Toysport]

Contaminate it with what?

 

.....i guess by mixing different oil weights

[BrandonsZ]

Yes mixing the oil weights will change the properties, the oil will become fully hybridized between the different types. I don't understand what it would be "contaminated" with.

 

Remember oil is made from distilled petrolium straight out of the ground and them additives such as deturgents and other modifiers are added. Mixing the different oils can be thought of as recombining it. Used oil can be distilled again and the products are pure straight weight oils which need to be recombined and additives added again to make the hybrid oils like 10w30 or 10w40.

 

Adding a poor quality oil to the good oil will dilute the good qualities of the mixture...

 

Ah just put 30W in and forget about it.

[Synlubes]

OIL: The True Story' date='

 

Synthetic oil should not be used in new engines because it does not allow the rings to seat properly, synthetic oil should not be used for the break in period or 10,000mi whichever is longer.

 

Otherwise 1 quart of synthetic mixed in 4 quarts of regular will give as much protection as full synthetic, but half the cost.[/quote']

 

1st - Conventional oils should be used for engine break in.

5,000 miles is enough of a "break in" period. After that, synthetics can be used. (Hopefully there would be a couple of oil & filter changes from new to 5,000 miles).

 

2nd - It is not recommended to mix synthetic and conventional lubes.

It can be done (if you have to) but you just lose the higher protection & properties of the syn-lubes when mixed with conventional lubes.

 

3rd - "1 quart of synthetic mixed in 4 quarts of regular will give as much protection as full synthetic, but half the cost."

 

half the cost = yes / same protection = no, see #2

 

New engines generate high wear metals to begin with and generally contain debris from machining and assembly. It is more beneficial to allow these wear metals to collect in an inexpensive motor oil than to circulate throughout the crankcase in a synthetic motor oil. Wear metals and manufacturing debris collect in the oil and filter and are then flushed out of the crankcase when drained. This allows for a much cleaner operating environment for synthetic lubricants to be installed.

 

For racing applications, a synthetic motor oil can be installed right away. These engines are frequently disassembled and rebuilt under more exacting conditions and require the improved wear protection of a synthetic motor oil.

[BrandonsZ]

Sorry, not "AS MUCH" protection, but how much "protection" do you need, and will 5 quarts full synthetic give you so much more protection that it's worth doing every XXXX miles?

 

In my experiance 4 qts of conventional and 1 qt of synth will have significantly less wear than straight conventional.

 

Replace you oil and filter on a new engine as follows.

 

100 miles. <-flush out the bad metal stuff

500 miles. <-check for bad bearings

1000 miles. <-double check for problems

2000 miles.

4000 miles.

6000 miles.

8000 miles.

10000 miles.

then every 2500+/-500 miles forever. This is within the breakdown limits for the worst SAE oil you can buy. Of course if you buy name brand at $1.50+/qt. then why not keep it in for a couple thousand more. But to get above 5k miles, you really need a good filter because that carbon starts to build up and could work like a slurry instead of a lubricant.

 

This will ensure all the metal is out of the engine and as good protection as possible. I also feel that you should wait 10,000 miles before adding synthetic, but if you don't believe me, tear the engine down after 5000 and see if the rings are seated, if so, go ahead. If not, wait 10k.

 

Back to oil...

 

So you could add just full synthetic, but then how often do you replace it? If you followed manufacturer's specs you'd think 7000k is fine, but not unless you buy the most expensive straight oil and the best quality filter. I buy cheapo filters and lowest quality (but SAE rated) straight oil, throw a quart of syntec in it and boom the oil feels different, the idle seems smoother, and the car runs better (subjective).

 

After two cars that both got over 200k before the first sign of burning oil I fell this works pretty good.

[technicalninja]

20 + years as an import car technician opinions-

Use standard oil for break in. first oil change at 600 miles (as long as you put together a "clean engine"). Second oil change at 3000 miles. At this change you can change to synthetic if you want. I fully believe that 90 percent of "break in" occurs in the first 15 min. I only use synthetic in turbos, cars that I think will have a long time between oil changes (playtoys, garage queens, show cars) and race engines.

Synthetics have two very important qualities above mineral base. They can withstand much greater heat (use in turbo and race cars) and they are very stable over a long time frame. Your engine is what gets the oil dirty and it will dirty up synthics at the same rate as mineral base. Do not believe the claims of reduced oil change intervals. Change it at 3-4000 miles. I use Castrol or Valvoline mineral base and Mobil 1 synthetic. I have seen the horror that can happen when mixing syn+mineral. Seals swell and gaskets fail. I do not mix ever. These occurances were a long time ago and supposibly the compatibility issues have been corrected but synthetic+mineral mix is why I rebuilt my first engine (76 Honda Accord 25 years ago). Old habits die hard.

Mixing weights should not cause a problem. I would not mix brands between oil changes. The multi weight oils are a marketing ploy. All oils are tested at 100 degrees centigrade with a standard viscosity gauge. They cannot be multigrade! They all have an additive package added to them to make them flow better at low temp. The additives can be different between brands and you might have a reaction between additive packages. This chance is very small.

I do not like oils with a parrifin base to them (Pennzoil, Quaker State, ect) but they work fine as long as you change the oil regularly. They tend to leave a waxy residue (my wife coined the name Godzilla Skin) and although I don't like the resultant mess it might have lubricating qualities of its own.

 

In the late 80s all manufacters jumped on the skinner bearings and rings band wagon. they used bearings of less width with tighter oil clearances to reduce friction thus increasing fuel economy. Increased OEM machine accuracyallowed this to happen. "Micro polished" internal parts used to be a selling by-line. Now almost all journals are micro polished from the factory. This design requires much thinner oils thus the almost universal change to 5W-30. This is a requirement on these engines. The use of too thick an oil can lead to engine failure from oil pump failure or bearings being "washed" out. Hydralic lifters designed to 5w-30 don't like thick oil either.

 

I always use the best oilfilter I can find. Factory or Wix is my first choice. Seen to many cheap ones blow off. You cannot understand how fast an engine can pump it's entire oil capacity out until you see it happen yourself! Makes a mess in the shop too.

 

Well that my 2 cents

[BrandonsZ]

I totally agree to what he has said, but I was taught on much older engines than 1980 and those engines are more sensitive to, or create more shavings and dirt. Just keep the oil changes frequent, don't go by that 7000 mile change interval that manufacturers are saying now. It just doesn't sould right, and remember, they want your engine to fail the day after the powertrain warrenty.

 

I think we have some good info here.

[blueovalz]

You cannot understand how fast an engine can pump it's entire oil capacity out until you see it happen yourself!

 

I improperly assembled an oil hose Aeroquip fitting on my Mustang (same engine as I now use in the BlueOvalZ) many years ago, and at that time, I was into piezo alarms and LEDs to warn me of loss of oil pressure (fortunately) on the motor instead of sole reliance on gauges. At 6K the alarm went off, followed immediately by smoke coming into the car. I shut it down immediately, coasted to a stop, and found the oil hose to the remote filters had blown off the fitting. The motor couldn't have run more than a few seconds before I shut it down, but in that time, it pumped more than 4 quarts out of the pan.

[BrandonsZ]

My 73 suburban with a 350sbc broke a connection to the piped factory oil pressure gage. Of course I had no idea and ran an estimated 1 mile at 35mph without oil (that's where the oil trail I left in the road stopped). The entire trip was only ~4 miles, but the oil started dropping with a huge puddle at about mile 1.5 and stopped other than a drip at mile 3. That's just the oil pressure gage and it was a tiny little brass line. The car engine survived and I didn't notice anything wrong with it the next 6 months I owned it.

[technicalninja]

You guys will like this incident.

Years ago I was changing the oil in a RX7 which has an oil filter which mounts upside down on the top of the motor. Well to drain oil out of filter before removal I punched 4 holes in it around the top (actually the bottom of filter and not in the center as you can waste a rotary that way- antidrain back valve can fall out of filer into engine). Well being in a hurry I negelected to change the filter. Filled the car with oil and started it. I knew I had a problem when one of the other techs yelled out "you've struck oil". I had 4 pencil thin brown lines extending from the open engine compartment to the cealing of the shop. Got it shut down in less that 10 seconds but had gone through about 3 quarts of oil. It dripped oil in my bay for days after!. I have not made this mistake again but everytime I work on a rotary I remember it.

[Guest Magnum Rockwilder]

Cool story, but considering the fliter is mounted on the back of the engine near the firewall and the hood only opens to about a 45 degree angle. I have a hard time digesting the logistics of the situation. Wouldn't the oil just hit the inside of the hood? I'm not trying to be a prick, I'm just having a hard time believing it so I thought I'd allow you to explain further.

[technicalninja]

First gen RX7 has hood that opens from rear like a Z. Made working on it much easier than 86 and up. This happened in either 83 or 84 when I was just a young punk. I have never forgotten to replace an oil filter since. Embarrasment is one of life's best instructors.