My 88 4Runner has the V6 and when it is cold it hovers around the half mark or a little higher, it will sit there like that until it warms up after about ten minutes. Once it warms up the needle hovers on the 1/4 mark at idle, and just north of the middle mark when above 1,800 rpm. I found out that if I run 10W-30 in the winter everything is fine until it warms up then the gauge barely moves above the 1/4 mark when going down the highway. I fixed that problem by running Toyota filters and I also run 10W-40 Conventional in the winter and HD 40 in the summer and it seems to like it, no excessive leaks or dry starts, but I am guessing that my engine has only around 200,000 miles on it, so try running a little thicker viscosity and see what happens. Also my uncle told me that running non-changing viscosity oil in the summer like HD-40 offers much better protection, because it contains more oil and less chemicals then changing viscosity oils. He seems to be right.
