Laminar and turbulent minimum ignition energies (MIEL and MIET) of a lean primary reference automobile fuel (PRF95; 95% isooctane/5% n-heptane) and air mixture at the equivalence ratio of 0.8 at 373 K with large Lewis number Le approximate to 2.95 >> 1 using small and large pin-to-pin electrode spark gaps (d(gap)) are measured in a dual-chamber, constant temperature/pressure, fan-stirred 3D cruciform burner capable of generating near-isotropic turbulence. Each MIE datum is statistically determined at 50% ignitability by 18-30 repeated runs over a range of ignition energy (E-ig). We find two ignition transition (IT) modes. (1) A non-monotonic IT at small d(gap) = 0.8 mm with the lowest MIET = 13.9 mJ (< MIEL = 30.1 mJ) occurring at a critical u'(c) approximate to 1.82 m/s due to the coupling effects between differential diffusion and turbulence, where u' is the r.m.s. turbulent fluctuating velocity. When u' > u'(c), MIET increases drastically (>> MIEL), because turbulence re-asserts its dominant role. (2) A regular IT at large d(gap) = 2 mm is found where MIEL is only 2.05 mJ, in which the increasing slopes of MIET with u' change from gradually to exponentially when u' > u'(c) approximate to 2.3 m/s. In the post-transition when u' >= u'(c), the averaged ratio of MIE at d(gap) = 0.8-mm and 2-mm (MIE0.8/MIE2.0) is 1.64 > 1, suggesting that using large d(gap) = 2-mm has a higher ignition probability than using small d(gap) = 0.8-mm for the lean-burn gasoline surrogate in intense turbulence. Finally, we estimate the uncertainties of burning velocities at u' = 0 and 2.76 m/s, which are respectively less than 2% and 6% when using small/large E-ig approximate to MIE/70 mJ and/or d(gap) = 0.8-mm/2-mm. These results are relevant to spark ignition gasoline engines operated in lean-burn turbulent condition. (C) 2020 The Author(s). Published by Elsevier Inc. on behalf of The Combustion Institute.