I've ran Mobil 1 10-30 for a year. Should I run 10-40 for summer? I love Mobil 1 and will stay with it. Stock motor just cams. ~420whp. E85.

 

You will have no issues sticking with what you have been using year round.

 

Read the following:


No. Multi-viscosity oils are designed to adjust their rate of flow (weight) based on outside and inside engine operating temperatures. When you read an oilcan that has a viscosity rating of 5W20 it means that the winter flow rate of the oil is 5 (thinner) than the summer flow rate (thicker). Multi-viscosity oils thicken up in the summer when the temps are hot and oil tends to thin out. When it gets cold they thin out in order to maintain optimum flow rate in all temperatures.

 

Yeah but a 10w30 oil is at an sae rating of 30 at operating temp which is thinner than the 10w40 sae would be at that same temp.

 

5W20 has viscosity indexers that causes the oil to thin more slowly with increasing temperature than straight weight oil. So, it starts out cold with the viscosity of 5 weight oil but when hot it has only thinned to 20 weight oil. Multi weight oils do not thicken.

Mitsubishi recommends 20W-40 weight oil for hot temperatures. Their reasoning is that they do not want owners using oil that contains enough viscosity indexer to produce 10W-40 oil. Viscosity indexer is not oil. However, since 20W-40 oil is about impossible to find on the store shelf, I use 10W-40.

 

^ 10W-40 over 20W-50 (when specifically looking for 20W-40 with no luck)??

 

No lucky is what you will have if looking of 20W40 oil. One thing I did find while searching the web is that Amsoil makes a 20W40 oil and it contains zero viscosity indexer. The oil, being synthetic, happens to meets the specification without any. The trouble is, it is for natural gas engines. If Amsoil would make this oil with an automotive additive package, there is our summer oil, hint hint.

 

Royal Purple FTW!

 

Yeah. You can also try 5w40 TDT if you like mobil 1.

 

Running e85 and 30 lbs like you are it won't hurt to run 10w40

 

^ this, just switch to the premium protection AMO 10-40

 

Stay with a good quality synthetic in a 5w-30. With oil technology as advanced as it is today you will we more than safe. Most race teams run 0w-30 in their race engines, granted they are more concerned about HP than longevity. Keep in mind that lighter weight oils flow better at start up and that is where most engine wear occurs. You will also get slightly better gas mileage using 5w over 10w. I have 80,000 on my 04 GRS and it sees redline daily. I use Mobil 1 5w-30 and change every 4000 miles, does not use any oil.

 

ive been using mobil 1 10w-30 since ive had the car and i was just curious i know just about everyone has a differnt approach to their car's oil. The 5w-30 makes since to me but idk if i want to go that thin in the summer even though youre prolly right it wouldn't hurt a thing its just a protection plan for me lol

 

Mitsubishi does not recommend 5W-30 for summer.

 

Since we are on the subject, I thought I would inform you all of this...

Most Advance Auto Parts stores are running a special on Mobil 1 right now. It is around $30 for 5 quarts and a Mobil 1 filter (saves you around $15 or so). I just picked up two oil changes the other day.

ALSO, the store up here clearanced out some Royal Purple in certain weights, 10W40 being one. So I picked up 10 quarts at $5.50 each! I would say I am stocked up for a while