- Joined
- Dec 16, 2022
- Messages
- 2
On many vehicles specifying an SAE 30 multigrade, 5w30 (as opposed to 10w30) used to not be recommended for anything except very cold places. Has this changed with the advent of modern synthetics?
I own three 1988-89 Toyotas (7MGE, 22RE) and a 1997 Subaru Legacy with a rebuilt N/A EJ22.
All of the manuals for these vehicles specify 10w30 or 10w40 for ambient temperatures from around 0*F to around 100*F.
They specify 5w30 for under 0*F but not for over around 60*F. Additionally, my Subaru's manual says 5w30 is "not recommended for high speed driving". High speed driving is not defined in any way. This is apparently a semi-common point of discussion among Subaru boards and owners of this gen model. Again this manual was written in '97.
I am in Western Washington and (possibly due to climate change) the winters have been getting colder (0-15*F highs, lower with wind chill) and the summers have been simultaneously getting hotter (over 100*F, especially in traffic).
Here is my question:
Can I trust a modern, full synthetic 5w30 year round in these vehicles, should I follow the manual and stick with a 10w30 in the summer or possibly all year, ...or should I look into something different still like a 5w40 or 0w40? How could I tell?
My guess as to why the 10w oils are recommended by the manuals (written in 1988, '89, '97, etc) is because the older 5w30 oils used to shear down more than the 10w's. According to my best research, the modern synthetic 5w30 oils we have simply don't have this problem anymore and are miles ahead of what they had when they wrote those manuals.
10w30 is harder to find, and I already have a large stock of M1 EP and EP HM 5w30. I'm also concerned about cold starts. This last winter was extremely cold (for where I live), but I felt very safe with the 5w in all my sumps. On the other hand I'm also concerned about my M1 5w30 not being adequate to protect in 104*F stopped traffic this summer.
I have already been running 5w30 year round in all three vehicles for several years with no issues (yet) but have not done any UOAs.
I also have a new 7MGE that just got built and I am very unsure of what oil to use in it after the break in. It is brand new. Builder recommended 10w30, but said 5w30 will "work". I believe the builder was simply following what the manual said and did not have any further reason for the 10w30 recommendation.
I don't race or drive my vehicles hard outside of a street setting, but I do drive them relatively hard on the street.
I am extremely on top of changing oil ahead of schedule based on mileage, engine hours, and trip length. I always stay on the low side of OCIs.
Has anyone else been in my situation? What viscosity should I choose? Keep the 5w30 and make it simple, or suck it up and start buying 10w30 or even something else in the interest of better engine protection? What could I do to better learn how to choose for myself? I'm completely lost on what I should decide on. I have also seen many conflicting opinions on this matter for each individual engine that I have in question.
Thanks.
I own three 1988-89 Toyotas (7MGE, 22RE) and a 1997 Subaru Legacy with a rebuilt N/A EJ22.
All of the manuals for these vehicles specify 10w30 or 10w40 for ambient temperatures from around 0*F to around 100*F.
They specify 5w30 for under 0*F but not for over around 60*F. Additionally, my Subaru's manual says 5w30 is "not recommended for high speed driving". High speed driving is not defined in any way. This is apparently a semi-common point of discussion among Subaru boards and owners of this gen model. Again this manual was written in '97.
I am in Western Washington and (possibly due to climate change) the winters have been getting colder (0-15*F highs, lower with wind chill) and the summers have been simultaneously getting hotter (over 100*F, especially in traffic).
Here is my question:
Can I trust a modern, full synthetic 5w30 year round in these vehicles, should I follow the manual and stick with a 10w30 in the summer or possibly all year, ...or should I look into something different still like a 5w40 or 0w40? How could I tell?
My guess as to why the 10w oils are recommended by the manuals (written in 1988, '89, '97, etc) is because the older 5w30 oils used to shear down more than the 10w's. According to my best research, the modern synthetic 5w30 oils we have simply don't have this problem anymore and are miles ahead of what they had when they wrote those manuals.
10w30 is harder to find, and I already have a large stock of M1 EP and EP HM 5w30. I'm also concerned about cold starts. This last winter was extremely cold (for where I live), but I felt very safe with the 5w in all my sumps. On the other hand I'm also concerned about my M1 5w30 not being adequate to protect in 104*F stopped traffic this summer.
I have already been running 5w30 year round in all three vehicles for several years with no issues (yet) but have not done any UOAs.
I also have a new 7MGE that just got built and I am very unsure of what oil to use in it after the break in. It is brand new. Builder recommended 10w30, but said 5w30 will "work". I believe the builder was simply following what the manual said and did not have any further reason for the 10w30 recommendation.
I don't race or drive my vehicles hard outside of a street setting, but I do drive them relatively hard on the street.
I am extremely on top of changing oil ahead of schedule based on mileage, engine hours, and trip length. I always stay on the low side of OCIs.
Has anyone else been in my situation? What viscosity should I choose? Keep the 5w30 and make it simple, or suck it up and start buying 10w30 or even something else in the interest of better engine protection? What could I do to better learn how to choose for myself? I'm completely lost on what I should decide on. I have also seen many conflicting opinions on this matter for each individual engine that I have in question.
Thanks.
Last edited: