Not to beat this subject to death.... be aware that SOME engine-designs have the bypass BUILT IN to some area of the engine-block. These engines DO NOT specify a filter with bypass.
For example, I know some Cummins engines have remote (to the filter) bypass valves. Infact, Cummins uses some 'tricks' to help the oil-pressure build up quickly when engine is started.... mainly because the injectors NEED oil-pressure to function. (Yes... some diesel engines use the engine-oil kinda like hydraulic fluid to operate the injectors.)
Most GM engines also have bypass-valve outside the filter.
Do not confuse the function of filter-bypass valve with the oil-pressure relief valve.... that is a different subject.
Actually, IMO, it is not a different subject.
The engine lubrication system has an over-pressure relief valve to prevent engine seals from being blown by an over-pressure event. Cold or Congealed oil might be a cause.
Oil filters have LARGE media area…and will pass cold oil because of that large area. The oil filter by-pass is solely for the purpose of preventing blockage of
the filter media …. to prevent media collapse….. which could dump trash into the engine… Nothing to do with protecting an engine
from over-pressure that already has an oil pressure relief of its’ own.
<edit: the following statement is incorrect…ignore please>
(A blocked filter does not starve the engine of lubricating oil because it is at the end of the system and is the return circuit. There is no danger of imminent loss of lubrication….The sump still supplies oil to the engine.)<end of edit>
Also, the assumption that a switch to synthetic oil is what solved your pull-start resistance is incorrect. As already evident…the resistance is due to oil
viscosity alone. Synthetic oils come if a variety of viscosity grades and the synthetic you selected likely had a lower viscosity. The term “synthetic” is not a magical word, it only denotes the degree of refinement of the “dino” oil base from which it is made.
If you had used a low-viscosity non-synthetic oil you’d have had the same result.
The “reason” most (not “all”) modern vehicles call for synthetic is to support their economical operating promotional statements that tout long oil change intervals. The synthetic oils not only commonly come in very low viscosity (W) grades… they do not shear/break-down as readily as “mineral” oils and therefore can be operated for longer intervals. Most (not “all”) modern vehicles still allow “mineral” oils…. just require the same shorter intervals vehicles required a few years previously.
italicized text above was altered for clarification