I agree with familyman and TresCrows on both topics. Most cars were 5w30 for the longerst time. Now due to EPA standards a thiner oil was needed and every car (lots) went to 5w-20. Now some are calling for 0w-20 oils.
I agree with familyman here.
</font><font color="blue" class="small">( Just FYI, the first number, in this case 5, refers to the base weight of the oil. The second number is what the additive package extends the viscosity to. If you want to up your base viscosity, switch to 10w30 or whatever you like. Also, the greater the number spread the more the additive package is making up for viscosity-wise on its own, ie; 10w40 has more viscosity extenders than 10w30, etc. Therefore, oils with a narrower spread (including single weight oils) are better protectors in high performance applications. Pure synthetics are the exception to this rule. If hot weather protection is a concern, go with a higher base number or try a pure synthetic. )</font>
I would use the world purity of the oil or less adds in an oil that as a larger spead or delta. As he stated this only works for group3 oils and below. The 100% synthetic oils (group 4 and 5) are a different world.
Now as 1075 stated (and I did a few days ago) that Mobil SUV and Delvac 1 are the same based on info on Mobil’s site.
Some people like Rotella and some like Mobil SUV (Delvac 1). Rotella is a group 3 hyrodro crack dino oil with a higher zddp. Mobil SUV has less ZDDP put a true group 4 oil.
If you are looking for high adds (ZDDP, P Vi) etc you can find better oils. But with better adds/better oil etc comes a higher price. Hence, you want better it is going to cost you.