I think it also depends on the condition of your engine too. If the motor has had some track work done in the pass, been drive hard, or high kms and not very well looked after you can expect leaks from any wore out seal. Because Castrol Egde is very thin oil though is a high flowing oil you can get a leak anywhere with old seals. From the sounds of him using i pretty thick 25w-40 oil maybe his given you that because it was something already in his work shop or his trying to hide a leak.
IMO if you drive it daily then 10w-30 FEO is fine as long as you change it every 5k. Even 10w-40 is fine as long as it gets changed every 5k.
I guess you could try castrol egde 5w-30 but be sure to check your oil levels all time to check for any leaks and to see if it burns up because its pretty thin.
Does the stop leak lubricant really works? Or its bullsh**??
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