Best Oil?
06-07-17, 12:17 PM
#1
Junior Member
Thread Starter
Best Oil?
I am sure this issue has been hammered to death, but I am interested to know what people use for oil in their RX7s. I have a super clean 1987 RX7 GXL with just 63K miles on it, all stock as far as I can tell. It will be a third/fun car for me so it will be driven occasionally to work or errands, but often just for fun, and will certainly stay off the roads in the frozen MN November - March. I saw in the owners manual it recommends 10W30 or 20W50 depending on the season. I know most synthetic is bad for rotaries, and see they recommend Idemitsu (sp?) racing oil on Mazdatrix. For a fun car that won't likely see much track time, is that worth doing? What do you all use?
06-07-17, 12:49 PM
#3
Junior Member
Thread Starter
06-07-17, 02:20 PM
#4
I use 20-50 in the summer and 10-30 in the winter, but I live in California and it never freezes here.
20-50 is of thicker viscosity than 10-30, so you don't want it in your car when it really gets cold, because motor oil acts like Maple syrup in that it thins out with heat and gets thicker in the cold.
10-30's fine.
20-50 is of thicker viscosity than 10-30, so you don't want it in your car when it really gets cold, because motor oil acts like Maple syrup in that it thins out with heat and gets thicker in the cold.
10-30's fine.
Yup. 
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07-21-17, 12:52 AM
#9
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Well, I've got a 1988 GTU with 250,000 miles (est) on the original engine and I have used two kinds of motor oil. I've had the car since new with 52 miles on her. My oils of choice:
- Valvoline VR-1 Racing, 20W-50 (Probably used most often.)
- Castrol GTX, 20W-40 and 20W-50 (later on)
Some may say 10W-30 may work year 'round, but the manual says you'll likely need up to 40W many times - temps above about 85 deg F. I had someone recommend the typical 10W-30 and I said "No thanks. Put in 20W-40." The 30 weight was my limiting factor and 20W never caused me any issues.
Oh ya, I live in SoCal / San Diego. It has always been garaged in the area but has been on many road trips around the west and parts of the US. That covers summer and winter trips, even going up for a few skiing trips.
Also, she's got a few thousand track miles, as well.
- Valvoline VR-1 Racing, 20W-50 (Probably used most often.)
- Castrol GTX, 20W-40 and 20W-50 (later on)
Some may say 10W-30 may work year 'round, but the manual says you'll likely need up to 40W many times - temps above about 85 deg F. I had someone recommend the typical 10W-30 and I said "No thanks. Put in 20W-40." The 30 weight was my limiting factor and 20W never caused me any issues.
Oh ya, I live in SoCal / San Diego. It has always been garaged in the area but has been on many road trips around the west and parts of the US. That covers summer and winter trips, even going up for a few skiing trips.
Also, she's got a few thousand track miles, as well.
07-21-17, 01:04 PM
#10
Information Regurgitator
I'm gonna be the oddball here. I've been running 10w40 year round for the past 12 years or so. I used to run Castrol GTX 20w50 then switched to 10w40 then switched to Havoline 'cause it was over $1 cheaper. I actually think I got 1 or 2mpg better after the switch to a lighter oil. I've been thinking of switching to the Shell Rotella 15w40 for the thicker base oil.
Where did you get 20w40 Castrol GTX? I've never seen it. They make a 20w40 for motorcycles but it's not the GTX product line. Did you mean 10W-40 or the 15w40 GTX for diesels?
- Castrol GTX, 20W-40
Some may say 10W-30 may work year 'round, but the manual says you'll likely need up to 40W many times - temps above about 85 deg F. I had someone recommend the typical 10W-30 and I said "No thanks. Put in 20W-40." The 30 weight was my limiting factor and 20W never caused me any issues.
Some may say 10W-30 may work year 'round, but the manual says you'll likely need up to 40W many times - temps above about 85 deg F. I had someone recommend the typical 10W-30 and I said "No thanks. Put in 20W-40." The 30 weight was my limiting factor and 20W never caused me any issues.
07-22-17, 08:13 AM
#11
07-22-17, 09:31 AM
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i've looked, and Mazda only specifies the weight. so no Mazda doesn't specify anything. empirical evidence shows us that the engine doesn't care what oil is in it, as long as there is some and its clean
07-22-17, 09:43 AM
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i'm jumping the gun a bit here, but its related. my boss mentioned that there were different oil filters, with different amounts of filtering for different oil change intervals.
so i looked, and they do. only bosch and wix (so far) have full information, and the cliff notes are these:
bosch and wix offer a normal filter which filters at ~20 microns. they then offer an "extended life" filter which, in bosch is 30, and then they offer a 40 mircon one too.
if you change your oil a lot, you should run the 20 mircon filter, and i like the tall one, which is Bosch 3323, Wix 51356.
if you don't change your oil run the Bosch extended D3323 at 40 microns.
i do not endorse either filter particularly, but these were the only two with fully published data, ie the factory filter is supposed to be really good, but no data. it is probably 30-40 microns with a lot of dirt holding capacity, because its designed for people who don't change their oil
so i looked, and they do. only bosch and wix (so far) have full information, and the cliff notes are these:
bosch and wix offer a normal filter which filters at ~20 microns. they then offer an "extended life" filter which, in bosch is 30, and then they offer a 40 mircon one too.
if you change your oil a lot, you should run the 20 mircon filter, and i like the tall one, which is Bosch 3323, Wix 51356.
if you don't change your oil run the Bosch extended D3323 at 40 microns.
i do not endorse either filter particularly, but these were the only two with fully published data, ie the factory filter is supposed to be really good, but no data. it is probably 30-40 microns with a lot of dirt holding capacity, because its designed for people who don't change their oil
07-22-17, 11:09 AM
#14
rotorhole
Rotella T 15W40, offers better protection when fuel dillutes the oil and has extra zinc additives for the turbine under the same circumstances if you have a turbo car.