No.
First the viscosity is wrong. SAE 30 is a single-grade motor oil. The 30 is a designation of the oil's viscosity grade according to the SAE. The 25W-50 is a multi-grade motor oil, meaning 25 grade viscosity in Winter (hence the "W") and 50 grade viscosity in normal operating conditions. If you wanted to match a multi-grade motor oil in viscosity to a SAE-30 grade oil, then you would need a multi-grade oil that had ended in 30, for example 10W-30.
Second, if you have been using a single-grade motor oil, you should not switch to a multi-grade because most single-grade motor oils do not have the detergent additives found in multi-grades. Switching to a multi-grade with a detergent present could suddenly dislodge gunk deposits creating a problem with solids and significantly decreased lubricant performance.
Now, with all that being said, if you drive a really old diesel truck and change your oil constantly, then the 25W-50 would probably be a great choice. Since the extreme pressure and heat in old vehicles tends to thins the oil, the high viscosity is probably helpful. And, if you change the oil often, the detergent will do you more good then bad.
If the recommended oil is SAE30 why would you use SAE 10W30? Some mowers recommend either of these weights but if your recommends 30W then using 10W30 will cause it to use oil.
No, absolutely not.
SAE30
The owner's manual for Oakes Man. L600 recommends using SAE30 motor oil in the chain cases.
Harley recommends their own Syn3 synthetic oil or their regular H-D brand 25W50 fossil oil (both made by Citgo), but I use & recommend Mobil One 15W50.
ANSWER:?SAE30 oil above 40 degrees F (4 C) and below this temperature use 5W-30
It is a little thick. You should use sae30 or 10w30 (on cold temperature)
If it has a Briggs and Stratton engine you need SAE30. If it is a Kohler it uses 10W30.
use SAE30 oil Recommended for use in veteran, classic and vintage cars, motorcycles and tractors which do not have the full flow type of oil filter. It is a low dispersant oil which allows the combustion chamber contamination to drop harmlessly into the sump
10W30 can be used, but SAE30 is best. 10W30 can run a bit hot, in warmer climates.
Briggs & Stratton small air cooled engines use SAE30 weight oil or SAE 10w30 if they will be operated in cold conditions. I highly recommend you use Synthetic oil in any air cooled engine.
If the manufacturer of the lawnmower specifies only SAE 30 then do not use SAE 10W-30. However on most mowers you can use either weight. I highly recommend you use synthetic oil in any air cooled engine.