What is the difference?

What exactly is the difference between SAE 30 oil and 10W-30? The book for my A suggests I use SAE 30, but all I can seem to find is 10W-30.

30 w is 30 w now matter what the temp outside 10/30 is 10 when cold 30 when at operating temp. I run 15/40 in my A all the time.

30 w is 30 w now matter what the temp outside 10/30 is 10 when cold 30 when at operating temp. I run 15/40 in my A all the time.

The 10w30 isnt made for tractors ,it might be ok for winter use. If you cant find sae30 then use 15w40 which is recomended for the newer tractors. I have switched every thing except for my truck and car to 15w40 and it works good in gas or diesel. Erik..

You can't be looking all that hard if you can't find 30W oil. Wal-mart has it as does TSC and any good auto parts store. Now as for the 10W-30 it is an oil that is in fact a 10W that acts like a 30W oil when hot. My self I use 30W in almost all my stuff. Shoot if you have an O'Reilly's auto part place close to you they have a 30W oil that is in fact Valvoline oil.

wal-mart is primarily where I've been looking. Our selection here is not the best in all the world. There is no TSC. I was looking late last night when the auto parts places were closed and wally-world was my only option. So, I'm hearing everyone say "no" to the 10W-30, right?

another thing is info.in those books is 50-60 yrs old. oils were straight grade then, and is not as common now adays.todays oils are a heck of a lot better than back then also.

Might add that the W means viscosity is tested at zero degrees F and thus 10W-30 is tested at zero and also at 212 degrees F for the 30 part of the equasion. They don't necessarily start with a 10 weight oil but rather use a pour point depressent to reach their viscosity goal on the low end and use viscosity index improvers to retain viscosity at the high temp. Also, there is a rather wide range that these oil have to fall into . In other words, one 30 wt oil may be at the low end of that scale and another may be at the high end. It is measured by a specified time it takes for a given amount of oil to flow through a particular size orfice at the temperature for that test. Most multi grade oils will be nearer the lower end of that scale and a straight wt will be on the higher end from the tests I have read. You have to read and interpet the specs on the oil container to see if it is acceptable for your particular engine.
As has been pointed out on these forums before, a lot of the newer oils are designed to reduce emisions and extend life of catalic converters so they reduced some of the additives that are desirable in a standard push rod type engine. Diesel engine oils still have the additives,(plus other specific to diesels) but can some times cause build up in heavy use gasoline engines thus the desire to use the low ash oils in those.

You should be able to get 30 weight oil most anywhere. On any multi viscosity oil, the actual oil is the viscosity oil of the lower number, with additives to make it perform like the higher number at higher temperature. For example 10w30 is 10 weight oil that acts like 30 weight at high temperature, 15w40 is 15 weight oil that acts like 40 weight at high temperature. For constant loads in warmer climates I would use the straight 30 weight. For cold starting and in cold temperatures I would use the multi grade 10w30 or 15w40.

Harold H