I switched my truck from mobil delvac 1300 15-40 to mobil delvac esp1 5-40 now my truck seems to not start as quick as it did with the 15-40 only about a second longer but I noticed it. Is this normal for a 7.3 with synthetic oil?Took it to a local shop and they hooked it up and tested everything and said everything is fine.The truck only has 65,000 miles on it.They told me it was probably the thinner oil and to go back to 15-40 synthetic the next time I change the oil.Has anyone ever heard of this?I seen they have schaefers 7000 15-40 at the local napa should I go to that a little more $ than iam paying for the mobil.